Priests of the Vedic religion are officiants of the yajna service. Yajna is an important part of Hinduism, especially the Vedas. Persons trained for the ritual and proficient in its practice were called ( 'regularly-sacrificing'). As members of a social class, they were generically known as 'sage' or 'seer'. Specialization of roles attended the elaboration and development of the ritual corpus over time. Eventually a full complement of sixteen s became the custom for major ceremonies. The sixteen consisted of four chief priests and their assistants. Chief priests The older references uniformly indicate the Writtiks and Purohits then as the presiding priest, with perhaps only the adhvaryu as his assistant in the earliest times. The phrase "seven hotars" is found more than once in the Rigveda. Hymn 2.1.2 of Rigveda states it as follows, The above hymn enumerate the priests as the , , , agnīdh, (meaning the maitrāvaruna) and adhvaryu. The was the reciter of invocations and litanies. These could consist of single verses (), strophes (triples called or pairs called pragātha), or entire hymns (sukta), drawn from the . As each phase of the ritual required an invocation, the had a leading or presiding role. The adhvaryu was in charge of the physical details of the sacrifice (in particular the adhvara, a term for the Somayajna). According to Monier-Williams, the adhvaryu "had to measure the ground, to build the altar, to prepare the sacrificial vessels, to fetch wood and water, to light the fire, to bring the animal and immolate it," among other duties. Each action was accompanied by supplicative or benedictive formulas (yajus), drawn from the yajurveda. Over time, the role of the adhvaryu grew in importance, and many verses of the were incorporated, either intact or adapted, into the texts of the yajurveda. The was a chanter of hymns set to melodies (sāman) drawn from the sāmaveda. This was a specialized role in the major soma sacrifices: a characteristic function of the was to sing hymns in praise of the invigorating properties of soma pavamāna, the freshly pressed juice of the soma plant. The was the reciter of hymns from the who was largely silent and observes the procedures and uses Atharvaveda mantras to 'heal' it when mistakes have been made. The term Brahman in the above hymn 2.1.2 refers to deity Agni of hymn 2.1.1. The rgvedic Brahmanas, Aitareya and Kausitaki, specify seven hotrakas to