In a few passages of the Rigveda mention is made of a celestial water-nymph called Apsaras ("moving in the waters"), who is regarded as the spouse of a corresponding male genius called Gandharva. The Apsaras, in the words of the poet, smiles at her beloved in the highest heaven. More Apsarases than one are occasionally spoken of. Their abode is in the later Vedas extended to the earth, where they especially frequent trees, which resound with the music of their lutes and cymbals. The Brahmanas describe them as distinguished by great beauty and devoted to dance, song, and play. In the post-Vedic period they become the courtesans of Indra's heaven. The Apsarases are loved not only by the Gandharvas but occasionally even by men. Such an one was Urvaçi. A dialogue between her and her earthly spouse, Pururavas, is contained in a somewhat obscure hymn of the Rigveda (x. 95). The nymph is here made to say:-- Among mortals in other form I wandered, And dwelt for many nights throughout four autumns. Her lover implores her to return; but, though his request is refused, he (like Tithonus) receives the promise of immortality. The Çatapatha Brahmana tells the story in a more connected and detailed form. Urvaçi is joined with Pururavas in an alliance, the permanence of which depends on a condition. When this is broken by a stratagem of the Gandharvas, the nymph immediately vanishes from the sight of her lover. Pururavas, distracted, roams in search of her, till at last he observes her swimming in a lotus lake with other Apsarases in the form of an aquatic bird. Urvaçi discovers herself to him, and in response to his entreaties, consents to return for once after the lapse of a year. This myth in the post-Vedic age furnished the theme of Kalidasa's play Vikramorvaçi. Gandharva appears to have been conceived originally as a single being. For in the Rigveda the name nearly always occurs in the singular, and in the Avesta, where it is found a few times in the form of Gandarewa, only in the singular. According to the Rigveda, this genius, the lover of the water-nymph, dwells in the fathomless spaces of air, and stands erect on the vault of heaven. He is also a guardian of the celestial soma, and is sometimes, as in the Avesta, connected with the waters. In the later Vedas the Gandharvas form a class, their association with the Apsarases being so frequent as to amount to a stereotyped phrase. In the post-Vedic age they have become celestial singers, and the notion of their home being in the realm of air survives in the expression "City of the Gandharvas" as one of the Sanskrit names for "mirage." Among the numerous ancient priests and heroes of the Rigveda the most important is Manu, the first sacrificer and the ancestor of the human race. The poets refer to him as "our father," and speak of sacrificers as "the people of Manu." The Çatapatha Brahmana makes Manu play the part of a Noah in the history of human descent.