Jaiminīya (Talavakāra) Brāhmaṇa 2-8.390

They strike away that darkness from his head. That Āditya is the twenty-first, the Viṣuvant; his rays are the Divākīrtyas themselves. Because these Divākīrtyas are [used], it is him that they surround with them, him that they make thrive. Concerning this they say: 'By what do the sitters of the year attain the heavenly world?' He should say: 'By this, that the Agniṣṭoma sāman is [chanted to the verse] "The head of heaven, the messenger of the earth".' By that. That which burns yonder is indeed the head of heaven; it is him that they ascend by this. Concerning this they say: 'Those who ascend him fall away from this world.' There is [the verse] 'the messenger of the earth'; this world is the messenger of the earth, and thus it is in this world that they stand firmly. The Agniṣṭoma sāman is the Bhāsa with ten stobhas; the Virāj has ten syllables, and the Virāj is food: [it is] for the attainment of food from the Virāj. However, those who perform the Agniṣṭoma sāman on these [verses] containing 'head' are liable to carry away food with their head for someone else. It should be performed only in the Anuṣṭubh. The Anuṣṭubh is speech; food is the ten stobhas. This speech is in the mouth; in this way they place food in their own mouth. Therefore it should be performed only in the Anuṣṭubh.

The Viṣuvant is the body of the year, with wings on both sides: that by which they go forward from here with the Abhīvarta,

and that pragātha by which they descend back from there, both of these they should perform on the Viṣuvant.

They place the two wings on the body itself for the purpose of flying to the heavenly world.