Different from that (body) made of prāṇa, more interior, is the Self made of mind. By it the former is filled. The Yajur-Veda is its head, the Ṛg-Veda its right wing, the Sāma-Veda its left wing, instruction is its body, the Atharva-Aṅgirasa hymns its tail and foundation.

This verse presents the third kosha: manomaya-kosha, the sheath made of mind (manas). It is subtler than prāṇa and directs it from within.

Manomayaḥ — made of mind. Manas in the yogic system is the processing mind, which receives sensory impressions, organizes them and generates responses. It is the level of thoughts, emotions, desires and imagination.

The bird structure here takes a surprising turn: it is formed by the Vedas:

• Yajur-Veda (head) — the sacrificial formulas, ritual action
• Ṛg-Veda (right wing) — the hymns of praise
• Sāma-Veda (left wing) — the melodic chants
• Ādeśa (body) — the teacher’s instruction, the Brāhmaṇas
• Atharva-Aṅgirasa (tail) — the fourth Veda, the magical mantras

Why do the Vedas form the mind? Because the mind is structured by what feeds it. In Vedic culture, the Vedas were the supreme content of the educated mind. In modern terms: our mind is shaped by education, culture, the texts we have internalized.

The manomaya-kosha is the domain of meditation in its early stages: learning to observe and calm thoughts, emotions, mental fluctuations (citta-vṛtti). But the Upaniṣad points out that even the mind, however subtle, is still a sheath. There is something even more interior.