Shatapatha Brahmana 7.5.1.9

7.5.1.9

athainamejayati | trīntsamudrāntsamasṛpatsvargānitīme vai trayaḥ samudrāḥ svargā lokāstāneṣa kūrmo bhūtvānusaṃsasarpāpām patirvṛṣabha iṣṭakānāmityapāṃ hyeṣa patirvṛṣabha iṣṭakānām purīṣaṃ vasānaḥ sukṛtasya loka iti paśavo vai purīṣam paśūnvasānaḥ sukṛtasya loka ityetattatra gaca yatra pūrve paretā iti tatra gaca yatraitena pūrve karmaṇeyurityetat

He then makes it move, with, 'Over the heaven-reaching three oceans he crept,' the three heaven-reaching oceans doubtless are these worlds, and over them he crept in the shape of a tortoise;--'the lord of waters, the bull of the bricks,' for he (the tortoise) indeed is the lord of waters, and the bull of the bricks;--'induing the covering of him, the well-made, in the world,' the covering (purîsha) means the cattle: thus, entering the (form of the) cattle of the well-made (Agni) in the world;--'go thither whither the former have passed away!' that is, go thither whither by this performance former (tortoises) went.