Matsya Purana 248.3

248.3

bhūyo'ṣṭadā bibhedāṇḍaṃ viṣṇurvai lokajanmakṛt.
cakāra jagataścātra vibhāgaṃ savibhāgakṛt .. 248.3 ..

This very egg was ripped open on its upper side by Lord Viṣṇu at the end of a thousand years; O king! The Creator then pierced the lower end of the egg, for the creation of Lokas.—2-3.

Again it was divided by Viṣṇu, the Creator and the great Divider, into eight parts The hole in the upper half of it became the sky, and that in the lower half formed the Pâtâla Kâmchanagiri was formed by the water that came out first of the egg created by Viṣṇu for the formation of the Lokas—4-5.