Jaiminīya (Talavakāra) Brāhmaṇa 2-8.415

'So according to the ritual rule this is to be undertaken: The brahman indeed is the head of the observance; heaven and earth are the two wings; the atmosphere is the trunk; the sāman is the tail. The Gāyatra [sāman] indeed is the head of the observance, for that is brahman. The Bṛhat and Rathantara are the two wings, for they are heaven and earth. The Vāmadevya is the trunk, for that is the atmosphere. The Yajñāyajñīya is the tail, for that is sāman. They praise the head with nine [verses]. Nine indeed are the vital breaths in a person. This is the measure of the breaths, the flourishing of the breaths. Upon it they superimpose the Gāyatra sāman. The Gāyatra sāman is indeed breath. Thereby they place breath in the head. Therefore breath is situated in the head. Having crept out westward, they praise with the 'head of Arka'. Those are the neck-vertebrae, since he sings as if narrating these worlds in order. Thereby he connects the head and the trunk. Therefore the head and the trunk are joined together. Regarding this they say: 'It becomes devoid of the twenty-five-fold [scheme] and redundant; therefore this should not be done here.'

With this threefold stoma they approach the Rathantara.

Brahman is indeed the threefold [stoma]; food is the Rathantara.

By means of brahman alone do they secure food.

Upon it they superimpose the fifteenfold stoma.

A thunderbolt indeed is the fifteenfold [stoma]; food is the Rathantara.

With the thunderbolt alone do they grasp food.

With this fifteenfold [stoma] they approach the seventeenfold.

The thunderbolt is the fifteenfold; the populace (viś) is the seventeenfold.

With the thunderbolt alone do they secure the populace.