Though the Çrauta Sutras are indispensable for the right understanding of the sacrificial ritual, they are, from any other point of view, a most unattractive form of literature. It will, therefore, suffice to mention in briefest outline the ceremonies with which they deal. It is important to remember, in the first place, that these rites are never congregational, but are always performed on behalf of a single individual, the so-called Yajamana or sacrificer, who takes but little part in them. The officiators are Brahman priests, whose number varies from one to sixteen, according to the nature of the ceremony. In all these rites an important part is played by the three sacred fires which surround the vedi, a slightly excavated spot covered with a litter of grass for the reception of offerings to the gods. The first ceremony of all is the setting up of the sacred fires (agni-adheya), which are kindled by the sacrificer and his wife with the firesticks, and are thereafter to be regularly maintained. The Çrauta rites, fourteen in number, are divided into the two main groups of seven oblation (havis) sacrifices and seven soma sacrifices. Different forms of the animal sacrifice are classed with each group. The havis sacrifices consist of offerings of milk, ghee, porridge, grain, cakes, and so forth. The commonest is the Agnihotra, the daily morning and evening oblation of milk to the three fires. The most important of the others are the new and full moon sacrifices (darçapurna-masa) and those offered at the beginning of the three seasons (chaturmasya). Besides some other recurrent sacrifices, there are very many which are to be offered on some particular occasion, or for the attainment of some special object. The various kinds of Soma sacrifices were much more complicated. Even the simplest and fundamental form, the Agnishtoma ("praise of Agni") required the ministrations of sixteen priests. This rite occupied only one day, with three pressings of soma, at morning, noon, and evening; but this day was preceded by very detailed preparatory ceremonies, one of which was the initiation (diksha) of the sacrificer and his wife. Other soma sacrifices lasted for several days up to twelve; while another class, called sattras or "sessions," extended to a year or more.