The most complicated and atypical of the śrauta sacrifices; nearly one third of the Śatapatha Brāhmaṇa (where it is associated with the ṛṣi Śāṇḍilya) is devoted to its exposition. Agnicayana probably began as an independent rite, which was then incorporated into the system of soma sacrifices; it is not obligatory at every soma sacrifice, but it is always combined with one. Its unique characteristic is that one of the offering altars (vedi), the uttaravedi, is constructed by piling up (cayana) five layers of fired clay bricks in the form of a bird of prey (śyena) (this is the only form to have been archaeologically attested, although other forms are theoretically possible). Built into this construction are the ‘heads’ of a man, a horse, a bull, a ram, and a he-goat, all of which can optionally be made of gold or clay. After this cayana, which is done with various offerings, the procedure of the soma sacrifice is followed. The sacrificer (yajamāna) who has performed agnicayana has to observe certain special vows for a year, with variations if he performs it more than once. The duration of the ritual, and the distribution of the rites over particular days, is not clear from the classical manuals, although some rites may have been extended over a year. It obviously entailed enormous expenditure. The Nambūdiri performance witnessed by the Indologist Fritz Staal (b. 1930) in 1975 was a compressed version lasting for twelve days. Symbolically, it appears to represent a ritual recreation of the original sacrifice of the cosmic man (Puruṣa/Prajāpati), through which the universe was created and ordered, and his re-ordering to ensure the continuity of the seasons and the well-being of the sacrificer. See also amṛtaciti.