Vishnupurana 4.4.5

4.4.5

tasmād asamañjaso 'ṃśumān nāma kumāro jajñe ||

SUMATI the daughter of Kaśyapa, and Kesiní the daughter of Rája Viderbha, were the two wives of Sagara. Being without progeny, the king solicited the aid of the sage Aurva with great earnestness, and the Muni pronounced this boon, that one wife should bear one son, the upholder of his race, and the other should give birth to sixty thousand sons; and he left it to them to make their election. Kesiní chose to have the single son; Sumati the multitude: and it came to pass in a short time that the former bore Asamanjas, a prince through whom the dynasty continued; and the daughter of Vinatá (Sumati) had sixty thousand sons. The son of Asamanjas was Anśumat.