Shatapatha Brahmana 6.2.3.8

6.2.3.8

te 'bruvan | upa vayamāyāmeti keneti yadeṣu lokeṣūpeti tatheti tadyadūrdhvam pṛthivyā arvācīnamantarikṣāttena devā upāyaṃstadeṣā dvitīyā citiratha yadūrdhvamantarikṣādarvācīnaṃ divastena 'rṣaya upāyaṃstadeṣā caturthī citiḥ

They said, 'We will step nigh!'--'Wherewith?'--'With what is over and above these worlds!'--'So be it!' Now what there is above the earth on this side of the air, therewith the gods stepped nigh, that is this second layer; and what there is above the air on this side of the sky, therewith the Rishis stepped nigh, that is this fourth layer.