Vishnupurana 4.24.36

4.24.36

tasmāddevabhūtiḥ //

Thus age after age Brahmans, Kshatriyas, Vaiśyas, and Śúdras, excellent Brahman, men of great souls, have passed away by thousands; whose names and tribes and families I have not enumerated to you, from their great number, and the repetition of appellations it would involve. Two persons, Devápi of the race of Puru, and Maru of the family of Ikshwáku, through the force of devotion continue alive throughout the whole four ages, residing at the village of Kalápa: they will return hither in the beginning of the Krita age, and, becoming members of the family of the Manu, give origin to the Kshatriya dynasties. In this manner the earth is possessed through every series of the three first ages, the Krita, Treta, and Dwápara, by the sons of the Manu; and some remain in the Kali age, to serve as the rudiments of renewed generations, in the same way as Devápi and Maru are still in existence.