Shatapatha Brahmana 8.7.1.17

8.7.1.17

sa purastātsvayamātṛṇāyai viśvajyotiṣamupadadhāti | dyaurvā uttamā svayamātṛṇāditya uttamā viśvajyotirarvācīnaṃ taddiva ādityaṃ dadhāti tasmādeṣo 'rvācīnamevātastapa tyatho prajananametadarvācīnaṃ taddivaḥ prajananaṃ dadhāti tasmādarvācīnamevātaḥ prajāyate

He lays down the Visvagyotis prior to the naturally-perforated one;--for the last naturally-perforated one is the sky, and the last Visvagyotis is the sun: he thus places the sun on this side (below) the sky, whence he burns only on this side thereof. But there also is generative power therein: he thus places generative power on this side of the sky, whence procreation takes place only on this side thereof.