Bhagavatapurana 3.11.39

3.11.39

vikāraiḥ sahito yuktair viśeṣādibhir āvṛtaḥ /
āṇḍakośo bahir ayaṃ pañcāśat-koṭi-vistṛtaḥ //

39. This (Egg of) universe comprised of the sixteen Vikāras or modifications and the eight Prakṛitis is fifty crores of Yojanas in breadth in the interior, and on the outside it is surrounded by seven sheaths of the earth and other Bhutas.