Verse 3.19.2

तद्यद्रजतं सेयं पृथिवी यत्सुवर्णं सा द्यौर्यज्जरायु ते पर्वता यदुल्बं समेघो नीहारो या धमनयस्ता नद्यो यद्वास्तेयमुदकं स समुद्रः ॥ ३.१९.२ ॥

tadyadrajataṃ seyaṃ pṛthivī yatsuvarṇaṃ sā dyauryajjarāyu te parvatā yadulbaṃ samegho nīhāro yā dhamanayastā nadyo yadvāsteyamudakaṃ sa samudraḥ || 3.19.2 ||

2. Of these two parts of the egg, the one that is silver is this earth, and the one that is gold is heaven. The thick membranes are the mountains. The thin membranes are the clouds and mist. The veins are the rivers, and the fluid in the bladder is the ocean.

Word-for-word explanation:

Tat yat rajatam, that [half] which is silver; sā iyam pṛthivī, that is this earth; yat suvarṇam, that [half] which is gold; sā dyauḥ, that is heaven; yat jarāyu, that which is the thick membrane; te parvatāḥ, they are the mountains; yat ulbam, that which is the thin membrane; sameghaḥ nīhāraḥ, are the clouds and mist; yāḥ dhamanayaḥ, that which are the veins;

Commentary:

It has already been stated that at a certain point in time the cosmos takes the shape of an egg, and after remaining in that state for a while, the egg splits in two. The lower part iṣ silver and represents the earth. The upper half is gold and represents heaven.

The thick outer membrane around the baby represents the mountains, and the thin inner membrane represents the clouds and mist. The veins of the infant are likened to rivers, and the fluid inside the bladder to the ocean.

It is to be noted that these diverse things have all come from one source.