Earliest extant text from the Vedic corpus, dated roughly between 1700 and 1200 BCE. Like the other Vedas, the Rigveda was orally transmitted in archaic Sanskrit for generations and considered to be the direct word or sound of God rather than authored by man. The text comprises ten books of 1,028 mantras in praise of various devas, or deities, the most prominent of which are Indra, the king of the gods, associated with thunder or lightning; Agni, the fire god, who especially represents the sacred fire of the Vedic yajna or ritual sacrifice; and Prajapati, the creator or father of the universe, known as Brahma in later texts. The Rigveda also contains the earliest textual reference to the four varnas of Brahmanical society, which later develop into what is now known as the caste system.