Taittirīya Upaniṣad · 8
अन्नादेव मनो जायते । मनसः सत्यसंकल्पादश्वमेधः । अश्वमेधाद्व्यृद्धिर्व्यृद्धेर्ध्रुवो ध्रुवादपरimiti श्रेष्ठो भवति श्रेष्ठः
annād eva mano jāyate | manasaḥ satyasaṃkalpād aśvamedhaḥ | aśvamedhād vyṛddhir vyṛddher dhruvo dhruvād aparimiti śreṣṭho bhavati śreṣṭhaḥ
From food the mind is born. From the mind with true intention arises the horse sacrifice. From the horse sacrifice prosperity, from prosperity constancy, from constancy the unlimited — thus the excellent becomes more excellent.
This anuvāka presents a causal progression connecting the physical with the transcendent. Beginning with anna (food), the physical substrate, the sequence ascends through increasingly subtle levels until reaching the aparimiti (unlimited).
Annāt manaḥ — From food the mind is born. This refers to the manomaya-kośa, the sheath made of mind, which depends on the physical body (which is nourished by food). The quality of the mind is directly connected with the quality of nutrition — not only physical but also subtle.
Satya-saṃkalpa — True intention. When the mind is purified and established in truth, its intentions (saṃkalpa) manifest powerfully. This is superior to any ritual sacrifice, including the great Aśvamedha (horse sacrifice).
The progression continues: from sacrifice arises prosperity (vyṛddhi), from prosperity constancy (dhruva), and from constancy the unlimited. This is the ladder leading from the conditioned toward the Brahman unlimited.
For the yogi, this indicates that spiritual progress is gradual — from body, to mind, to purified intention, to the realization of the unlimited.