Shatapatha Brahmana 7.5.1.36

7.5.1.36

taṃ vā etam | ita ūrdhvam prāñcaṃ cinotyasau vā āditya eṣo 'gniramu tadādityamita ūrdhvam prāñcaṃ dadhāti tasmādasāvāditya ita ūrdhvaḥ prāṅ dhīyate

Now that (Agni) he builds upwards from here (as flying) towards the east, and that Agni being yonder sun, he thereby places yonder sun upwards from here in the east; whence yonder sun is placed upwards from here in the east.