Overview
The uṣṇīṣa is one of the thirty-two physical marks of a great being. It is a feature of the head, and in its simplest form it seems to refer to the shape of the head as being “like a turban,” the original meaning of the Sanskrit, indicating a majestic, raised cranial vault, perhaps of increased convexity or with an apical point. More elaborately it refers to a dome-shaped extension of the top of the head, a crest that is either anatomical (bone or flesh) or made of hair.
There is an additional characteristic of the uṣṇīṣa unique to tathāgatas, mentioned in a number of texts and narratives and included in at least one atypical list of the eighty minor signs: that its top, or its extent, is “invisible” or “out of sight.” 
The way that the uṣṇīṣa has been understood as a sign of buddhahood may well have been influenced by how artists attempted to represent it as sculpture and painting came to be used to depict the Buddha’s physical appearance. Perhaps more than any of his other features, the uṣṇīṣa remains the one that makes depictions of the Buddha instantly recognizable to most people everywhere, regardless of culture.
As an aspect of the Buddha’s rūpakāya and hence of the physical fruition of his vast accumulated merit, the uṣṇīṣa is said in particular to result from the respect he has shown to parents, teachers, and other worthy persons using his head by bowing down, touching his head at their feet, prostrating himself to them, and similar gestures.
The Buddha’s uṣṇīṣa is also mentioned as the source of protective dharaṇīs and of a number of deities related to those dhāraṇīs in works generally classified among the Action Tantras (kriyā).
Etymology
The Sanskrit uṣṇīṣa in general usage (e.g. in the Brāhmaṇas) denotes a turban, headband, or other cloth wound around the head. But in the context of the thirty-two marks of a great being (mahāpuruṣalakṣaṇa), and in reference to the Buddha’s physical characteristics, it specifically refers to one of the physical features of his head.
Place in the List of Thirty-Two Marks
The many lists of the thirty-two marks in canonical texts do not all follow the same order. Among them, the uṣṇīṣa takes different places in the order and is listed as follows:
first in the list given in The Play in Full (Toh 95) chapter 7, (but thirty-first in chapter 26), and first in the Mañjuśrīparipṛcchā (Toh 172).
twenty-third in the lists given in the three long Prajñāpāramitāsūtras, the Hundred Thousand (Toh 8), Twenty-Five Thousand (Toh 9), and Eighteen Thousand (Toh 10) line sūtras, and in the Abhisamayālaṃkāra (Toh 3786, VIII.16);
twenty-eighth in the list in the Ratnagotravibhāgottaratantraśāstra (Toh 4024);
thirty-first in the lists in the Saṅghabhedavastu (Toh 1, ch. 17, F.284.a) and in Asaṅga’s Bodhisattvabhūmi (Toh 4037, III.5.5);
last in the Pali Lakkhaṇasutta (DN 30), in The Good Eon (Bhadrakalpika, Toh 94) at 2.164 et seq., and in the list in The Transcendent Perfection of Wisdom in Ten Thousand Lines (Toh 11);
In most of these texts the mark is indicated by the phrase uṣṇīṣaśīrṣa or uṣṇīṣaśiraskatā (Pali uṇhīsasīso), in Tibetan dbu gtsug tor dang ldan pa.
The Uṣṇīṣa’s Meritorious Causes
Some of these texts include explanations of the Buddha’s specific past meritorious actions that have caused each of the marks to appear, and in the case of the uṣṇīṣa this is said to be through his having respected parents, teachers, and other worthy persons by bowing his head to their feet. Outside accounts of the thirty-two marks as a whole, the Buddha’s statement in The Questions of Dīrghanakha the Wandering Mendicant (Toh 342) at 1.22 follows the same pattern. A passage in The Good Eon (Bhadrakalpika, Toh 94) at 2.193 enumerates the different features of the uṣṇīṣa brought about as the fruition of the six perfections (see below).
The uṣṇīṣa seems to be among the highest valued of the thirty two marks. Regarding the proportional amounts of merit the different marks represent, the Ratnameghasūtra at 1.234 lists an increasing order of magnitude for one of the Buddha’s hair follicles, then the first twenty-nine marks in general, then the urṇa hair, and then the uṣṇīṣa, each requiring immense multiplications of the preceding amount of merit to appear, and only finally outdone by the Buddha’s voice. This gradation of merit is reiterated by Asaṅga in his Bodhisattvabhūmi (Toh 4037), III.5.5. That the Buddha’s voice is accorded such importance is no great mystery, given what he can accomplish with it. But if such gradations in terms of merit are correlated with importance in terms of Buddha-activity, the fact that the uṣṇīṣa comes in second place only to his voice would suggest that its functions go far beyond a distinguishing mark, and this may be related to the aspects mentioned below of its emanation of lights and protective deities.
Descriptions and Interpretations of the Uṣṇīṣa
For two or three centuries after the Buddha’s lifetime, there seems to have been little direct artistic representation of his physical appearance, which was evoked only in images of footprints, and of symbolic objects like the tree of awakening or the doctrinal wheel. The earliest known depictions of the Buddha’s body are second century BCE sculptures from Gandhāra, produced perhaps with cultural influence coming from, or shared with, the Greeks. In these, the uṣṇīṣa is commonly depicted as a raised, rounded area of his luxuriant hair, or as a bound chignon..jpeg)
While the artistic iconography, starting with those first Gandhāran images, has no doubt influenced what the uṣṇīṣa is understood to look like and what it might be made of, oral and textual descriptions are probably much older than the earliest depictions by artists. Yet different texts interpret the uṣṇīṣa in a range of different ways. To begin with, depictions suggesting long hair would be misleading if, as most textual accounts suggest, the Buddha’s head was shaven. No texts suggest that he ever again grew the long hair that, as Prince Siddhartha, he had cut off after renouncing the kingdom. It seems more likely that instead he had short, tightly curled ringlets of bluish-black dark hair. Details of its color, thickness, smoothness and so forth are given in no less than six items in the list of eighty minor signs often found together with the thirty-two major marks.
In the Pali tradition, the statement for this mark in the Lakkhaṇasutta, “mahāpuriso uṇhīsasīso hoti,” is taken, reasonably enough, to mean “The great being has a head shaped like a turban” (Bhikkhu Sujato’s translation) or “His head is like a royal turban” (Rhys Davids).
Hence, Edgerton:
“…according to Pali Dīghanikāya commentary ii.452.1 ff. having a head the size and shape of which makes it seem turbanned.”
Rhys Davids (1910, 16, n. 4) says “This expression, says the Cy., refers to the fullness either of the forehead or of the cranium. In either case the rounded highly-developed appearance is meant, giving to the unadorned head the decorative dignified effect of a crested turban, and the smooth symmetry of a water-bubble.”
Textually, therefore, the Pali tradition follows commentaries in predominantly noting the symbolic significance of this mark regarding leadership without emphasizing anything abnormal about it as describing the particular shape of the Buddha’s head. Nevertheless, sculpted and painted images of the Buddha Śākyamuni in South-East Asia almost universally show a pronounced uṣṇīṣa in the form of a protuberance at the crown of his head (this is often surmounted by a long, pointed finial in the shape of a flame or jewel, representing spiritual power, and not strictly part of the uṣṇīṣa).
In the (early) Mahāyāna tradition, the long Prajñāpāramitā sūtras all contain lists of the thirty-two marks including the uṣṇīṣa but without detailed descriptions. The commentaries appear to follow the simpler interpretations of the uṣṇīṣa, as in the Pali texts, as a description of the shape of the head, or the intermediate interpretations describing a fleshy crest extending over the head from one ear to the other. Thus in The Long Explanation of the Noble Perfection of Wisdom in One Hundred Thousand, Twenty-Five Thousand, and Eighteen Thousand Lines (Prajñāpāramitābṛhaṭṭīkā, Toh 3808), at 5.1327:
“…Have an uṣṇīṣa on the top of their head. Take this as a head like a bound turban.1 It is explained that the heads of others are not fully developed, are elongated or squashed and are not symmetrical. The heads of great persons are arranged evenly like a turban, spherical, completed, well-shaped, and well developed.
Others say this major sign is to teach that the forehead is fully developed in size. The flesh in between and above the right ear and the left ear of the foreheads of great persons is well shaped; the size of the forehead is fully completed and beautiful like a royal golden turban that has been bound on.
“Again, the former action [resulting in this sign] is that they were the first, they were chief, at performing all wholesome actions, making parks, assembly halls, places to quench thirst and so on, therefore they have a build like a fig tree; and an uṣṇīṣa on the top of their head because, having become chief in the assembly they raised their head uncowed, and fearlessly enjoined these actions on others. Hence these are signs that presage holding the highest office.”
Likewise, a mention of the uṣṇīṣa in The Questions of Dīrghanakha the Wandering Mendicant (Toh 342) at 1.22 uses the phrase gtsug tor ’phags pa , “raised uṣṇīṣa,” for which the attested Sanskrit is uṣṇīṣonnata.
There are nevertheless more elaborate interpretations. As Edgerton continues: 
“But in Buddhist Hybrid Sanskrit (and Pali) interpreted as having a head surmounted by an excrescence, whether a top-knot of hair, or a growth in the skull. So Tibetan regularly (uṣṇīṣa = gtsug tor), e.g. in Mahāvyutpatti 236 uṣṇīṣa-śiraska-tā. Confirmed by Gaṇḍavyūha 401.26 ff. mūrdhni cāsyoṣṇīṣam abhinirvṛttam abhūt, sujātaṃ samantaparimaṇḍalaṃ madhyābhinyastakeśālaṃkāraṃ koṭīśatasahasrapattraratnapadmasaṃdarśitaṃ samantāt samabhāgapratiṣṭhitam aparimitamahārghyatāpradhānamadhyam.”
This mention in the Gaṇḍavyūha of which the Sanskrit is cited by Edgerton is a description of the uṣṇīṣa as twenty-seventh of the thirty-two marks enumerated by Gopā as being seen on Prince Tejodhipati, found in Chapter 43 (43.93):
“There was an uṣṇīṣa formed on the crown of his head: it was well formed, perfectly round, central, an adornment of the hair, resembling a precious lotus with a trillion petals, perfectly symmetrical, and cherished as a priceless crest adornment.”
Another more detailed description is found in The Good Eon (Bhadrakalpika, Toh 94) at 2.193), where (as for all the thirty-two marks of a great being) six features of a buddha’s uṣṇīṣa are listed as the fruits of the six perfections practiced by him as a bodhisattva:
“What are the bodhisattvas’ six perfections that bring about his possessing the uṣṇīṣa on his head? As the ripening of the perfection of generosity it is a deep blue coil. As the ripening of discipline, it coils to the right. As the ripening of patience it is untouched by dust. As the ripening of diligence its summit cannot be seen. As the ripening of concentration it is an object of constant gaze. As the ripening of the perfection of insight it is unaffected by rain or wind. It is in these ways that the six perfections of the bodhisattvas bring about his possessing the uṣṇīṣa on his head.”
Among the various kinds of relics to which pilgrims in Gandhāra could pay their respects in the middle of the first millennium, as witnessed by the great Chinese travelers Faxian and Xuanzang, were the Buddha’s “uṣṇīṣa bone,” suggesting that in at least some Buddhist communities of the time it was seen as a distinctive anatomical feature of the cranium.2
The Anavalokitamūrdhatā, the Vertex that is Out of Sight
An additional characteristic of the uṣṇīṣa (perhaps attributable only to tathāgatas and not to other kinds of great being) is found in many Mahāyāna texts, as exemplified by the phrase regarding diligence in the passage 2.193 from The Good Eon (Toh 94) cited above. The most common formulation in Sanskrit is anavalokitamūrdhatā (literally “the head / top of the head is not looked upon / beheld”), rendered almost constantly in Tibetan spyi gtsug bltar mi mthong ba or spyi gtsug bltar mi mngon pa (“the crown of the head looked at is not seen”). It is often translated “the invisible crown” or “invisible cranial summit.”
This feature is included as seventy-first in the lists of the eighty supplementary signs in The Transcendent Perfection of Wisdom in Ten Thousand Lines (Toh 11) at 2.69 (unusually, with the alternative formulation gūḍhaśikhatā / spyi gtsug bltar mi mngon pa) and at 29.57 (with the usual rendering), but the lists in the other Prajñāpāramitā sūtras3 and most such lists in other canonical texts do not include it.
According to Lamotte’s Traité:
This is what the Bodhisattvabhūmi says, p. 381: tatroṣṇīṣaśiraskatānavalokitamūrdhatā caikamahāpuruṣalakṣaṇaṃ veditavayaṃ tadvyatirekeṇānupalaṃbhāt (“the two make up a single mark of the Great Man; there is no difference between them.”)
The anavalokitamūrdhata is mentioned as third in a list of ten superiorities (of which the first two are the major marks and supplementary signs respectively) in the Ratnacūḍaparipṛcchā (Toh 91, F.228.b), and as a mark of the tathāgatas requiring even more merit than the thirty-two marks in The Teaching of Akṣayamati (Toh 175, 1.103).
Elsewhere in the sūtras, it is at times mentioned in association with the uṣṇīṣa itself, as in the Bhadrakalpika (Toh 94, 2.193), The Play in Full (Toh 95) at 26.172 and in The Questions of Gaganagañja (Toh 148, F.263.a); but more often on its own, as in Upholding the Roots of Virtue (Toh 101, 4.21, 4.75, 8.61, 10.136, 13.91), the Pratyutpannabuddhasaṃmukhāvasthitasamādhisūtra (Toh 133, F.24.a), The Teaching on the Great Compassion of the Tathāgata (Toh 147, 2.263), The Perfection of Generosity (Toh 182, 2.74), The Seal of Engagement in Awakening the Power of Faith (Toh 201, 1.423 and 1.464-5, see below), and other sūtras.
Its significance may sometimes be understood as metaphorical in nature—that because of the Tathāgata’s uniquely superior qualities no other living being may look down upon him from above. With regard to depictions of the Buddha and Avalokiteśvara, Schopen adopts that interpretation.4 This may also be seen as a prohibition, the sanctions for breaking which are one of the themes investigated by Durt. Another interpretation mentioned by Durt as found in Chinese Mahāyāna sources is that the uṣṇīṣa emits light so bright that it cannot be looked at.5
But anavalokitamūrdhata appears more often to be presented as a more literal description of how the uṣṇīṣa extends upwards, physically, to a height so vast that most kinds of beings either cannot see its top, or cannot see it at all. In The Seal of Engagement in Awakening the Power of Faith (Śraddhābalādhānāvatāramudrāsūtra, Toh 201) at 1.464-5, Samantabhadra’s explanation to Mañjuśrī makes it clear that the mention of the term refers to the physical height of a tathāgata, even if the imagery of that passage may also, no doubt, convey a metaphorical message regarding stature.
The impossibility of the top of the uṣṇīṣa being seen—again, in contrast to some sort of prohibition—is so much a law of nature that it is used as an example of something “untenable” (gnas med) in The Teaching on the Great Compassion of the Tathāgata (Toh 147, 2.263).
In some texts the uṣṇīṣa is said to extend upwards so that even when the Buddha is on earth in the human realm, the top of his uṣṇīṣa is in the realm of the gods.
The most complete example is found in the seventh chapter, on the mysteries of the Tathāgatas’ body, of The Secrets of the Realized Ones (Tathāgatācintyaguhyanirdeśa, Toh 47) where (7.14 et seq.) the story is told of a bodhisattva from another buddhafield who came to venerate the Buddha soon after his enlightenment, and using his supernatural powers tried to see the top of the Buddha’s crown by travelling upwards. But even travelling upwards through countless other buddhafields was not enough for him to be able to do so. However, the story ends more on a note of the inconceivability of a tathāgata’s body than of any more physical dimensionality.
Lamotte’s Traité adds several examples of stories that imply the physical impossibility of the top of the uṣṇīṣa being seen, some evidently from the Pali—significant, as the anavalokitamūrdhatā is usually said to be a purely Mahāyāna notion. The passage quoted here is from Gelongma Karma Migme Chödrön’s English translation (ch. 26, appendix 2):
“When the Traité says here that nobody can see the top of the Buddha’s cranium and that nobody among gods and men can surpass him, it should be taken literally: the uṣṇīṣa of the Buddha is invisible and nobody can go above it. This explains several mysterious episodes in the Buddha’s life.
“When the recluse Asita wanted to examine the new-born Buddha, the baby’s feet turned upside-down and placed themselves on the chignon of the recluse (bodhisattvassa pādā parivattitvā tāpasassa jaṭāsu patiṭṭhajiṃsu). (cf. Nidānakathā in Jātaka, I, p. 54, l. 25–26.)6
“ ‘When Gautama travels, heavenly gifts, precious parasols and flowers rain down like snow. The devas, nāgas and flying birds do not dare to fly above him for, among beings of the threefold world, none can see the summit [of his cranium]’; (cf. Brahmāyuḥsūtra, T 76, p. 884a16–18.)
“Sātāgira and Hemavatā who were flying to an assembly of yakṣas were stopped in full flight and forced to land because, if they had continued on their route, they would have passed above the Buddha. (cf. Comm. on the Suttanipāta, I, p. 221–223; Comm. on the Hemava, p. 64.)
“Near Rājagṛha, at Yaṣṭivana ‘Perch Forest’: ‘Once a Brahmin, having heard that the Buddha’s body was sixteen feet high, persisted in doubting and did not believe it. He wanted to measure the Buddha with a bamboo rod sixteen feet long, but the Buddha’s body constantly rose above the top of the rod and surpassed sixteen feet. He continued growing so that the Brahmin, quite unable to reach the true height, threw away his stick and went away. As a result of this event, the bamboo stick remained planted in the ground and took root there.’ This anecdote is told by Hiuan-tsang in the Si-yu-ki, T 2087, k. 9, p. 920a7–12, and is represented on the bas-reliefs at Gandhāra (Foucher, Agb. p. 505, pl. 251b; p. 522, pl. 256c) but has left no trace in the texts. However, a canonical passage should be noted where the Teacher forbade everyone except himself to measure a pudgala: Mā puggalesu pamāṇikā ahuvatthu … yo vā pan’assa madiso, “Do not be one of those who measure men, for the person who takes the measure of men wounds himself. It is I who am able to take the measure of men, or someone like me.” (Anguttara, III, p. 350, 351; V, p. 140, 143; Tsa a han, T 99, k. 35, p. 258a23–25; 258c7–8; Śūraṃgamasamādhi, p. 208; Śikṣāsamuccaya, p. 92). …
“For other comments, see H. Durt, Note sur l’origine de l’Anavalokitamūrdhatā, Indian and Buddhist Studies, XVI, p. 1967, p. 443–450.”
The Uṣṇīṣa and the Buddha’s Smile
When the rays of light emanated by the Buddha from his smile return to him from the realms and world-systems they have permeated, if they vanish into the uṣṇīṣa it is a sign that he is about to prophesy the unsurpassed perfect awakening of a future buddha.
The Source of Rays of Light
The Source of Deities
In the Kriyātantras and dhāraṇī-sūtras, as well as in the Kalacakra, the uṣṇīṣa is described as the source (’byung gnas) of certain deities, mainly protective. However, we have not so far identified a clear and explicative founding narrative for this trope.
In both The Root Manual of the Rites of Mañjuśrī (Mañjuśrīmūlakalpa, Toh 543) and the Vimalaprabhā (Toh 845), uṣṇīṣa deities include Vijayā, Sitātapatra, and the cakravartin deities.
In Titles of Texts
The words uṣṇīṣa or gtsug tor appear as elements of the full title of some canonical texts. In some cases, this is directly linked to the uṣṇīṣa being the source of the deity or dhāraṇī concerned, e.g. for Uṣṇīṣavijayā or Uṣṇīṣasitātapatrā (see above).
In other cases, the term may perhaps be used as a metaphor for importance or unsurpassability. For example, the long title in Tibetan of the Śūraṃgamasūtra is bcom ldan ’das kyi gtsug gtor chen po de bzhin gshegs pa’i gsang ba sgrub pa’i don mngon par thob pa’i rgyu byang chub sems dpa’ thams cad kyi spyod pa dpa’ bar ’gro ba’i mdo.