Atharvaveda 9.5.20

9.5.20

ajó vā́ idám agne vy àkramata tásyóra iyám abhavad dyáuḥ pr̥ṣṭihám |
antárikṣaṃ mádhyam díśaḥ pārśvé samudráu kukṣī́ ||20||

The goat verily strode out here (idám) in the beginning; this [earth] became its breast, the sky its back, the atmosphere its middle, the quarters its (two) sides, the (two) oceans its paunches;