At SB 3.6.6 the golden Person is described as dwelling 'ANDakoshe', in the shell of the egg, in the waters: 'ANDakosha uvAsApsu sarva-sattvopabR^iMhitaH', accompanied by all beings.
Andakosha
अण्डकोश
Also known as Anda-kosha (the shell of the cosmic egg)
Andakosha is the shell of the cosmic egg in which the golden Person dwells in the waters. At SB 3.6.6: 'hiraNmayaH sa puruShaH sahasra-parivatsarAn / ANDakosha uvAsApsu sarva-sattvopabR^iMhitaH' — that Person, golden, dwelt a thousand cycles in the shell of the egg, in the waters, accompanied by all beings. At SB 3.6.7 he is called the embryo of the world's creators, who divides himself onefold, tenfold and threefold.
Śrīmad Bhāgavata Mahāpurāṇa 3.6.6 — Sanskrit Wikisource (pinned chapter page; Devanagari from the cross-validated transcription in validation/sanskrit_skandha3.json)
At SB 3.11.39 the egg's shell is described as joined with its transformations and covered by the particular and the rest, extending fifty koti beyond. At SB 3.11.40 it is said that the Lord has entered like an atom and that other heaps of eggs too are seen in crores.