Shatapatha Brahmana 8.7.1.15

8.7.1.15

atha viśvajyotiṣamupadadhāti | ādityo vā uttamā viśvajyotirādityo hyevāmuṣmiṃloke viśvajyotirādityamevaitadupadadhāti

He then lays down a Visvagyotis (all-light brick);--the last Visvagyotis, doubtless, is the sun, for in yonder (celestial) world the sun, indeed, is 'all the light': it is the sun he thereby sets up.