Markandeyapurana 73.12

73.12

caturyugānāṃ saṃkhyātā sādhikā hyekasaptatiḥ /
kṛtatretādisaṃjñānāṃ yānyuktāni yuge mayā //

Very powerful and valiant were that Mann’s sons, renowned, like unto the thirty gods. The descendants of his sons ruled over the earth as kings during the manvantara of that Manu of supreme splendour. Of his four ages were reckoned in truth seventy-one and a half, of the ages called Ṛrita, Tretā and so on, which I have declared in the account of the Age. By the innate splendour of the austerities of that most excellent high-souled Manu his seven sons became the seven ṛṣis in that period.