A very sacred ceremony that can be connected with the soma sacrifice is the Agnichayana, or "Piling of the fire-altar," which lasts for a year. It begins with a sacrifice of five animals. Then a long time is occupied in preparing the earthenware vessel, called ukha, in which fire is to be maintained for a year. Very elaborate rules are given both as to the ingredients, such as the hair of a black antelope, with which the clay is to be mixed, and as to how it is to be shaped, and finally burnt. Then the bricks, which have different and particular sizes, have to be built up in prescribed order. The lowest of the five strata must have 1950, all of them together, a total of 10,800 bricks. Many of these have their special name and significance. Thus the altar is gradually built up, as its bricks are placed in position, to the accompaniment of appropriate rites and verses, by a formidable array of priests. These are but some of the main points in the ceremony; but they will probably give some faint idea of the enormous complexity and the vast mass of detail, where the smallest of minutiæ are of importance, in the Brahman ritual. No other religion has ever known its like. As the domestic ritual is almost entirely excluded from the Brahmanas, the authors of the Grihya Sutras had only the authority of popular tradition to rely on when they systematised the observances of daily life. As a type, the Grihya manuals must be somewhat later than the Çrauta, for they regularly presuppose a knowledge of the latter. To the Rigveda belongs in the first place the Çankhayana Grihya Sutra. It consists of six books, but only the first four form the original portion of the work, and even these contain interpolations. Closely connected with this work is the Çambavya Grihya, which also belongs to the school of the Kaushitakins, and is as yet known only in manuscript. Though borrowing largely from Çankhayana, it is not identical with that work. It knows nothing of the last two books, nor even a number of ceremonies described in the third and fourth, while having a book of its own concerning the sacrifice to the Manes. Connected with the Aitareya Brahmana is the Grihya Sutra of Açvalayana, which its author in the first aphorism gives us to understand is a continuation of his Çrauta Sutra. It consists of four books, and, like the latter work, ends with the words "adoration to Çaunaka."