BṚHADĀRAṆYAKA UPANISHAD · 1.2.6

सो ऽकामयत -- भूयसा यज्ञेन भूयो यजेयेति ।
सो ऽश्राम्यत् ।
स तपो ऽतप्यत ।
तस्य श्रान्तस्य तप्तस्य यशो वीर्यम् उदक्रामत् ।
प्राणा वै यशो वीर्यम् ।
तत् प्राणेषूत्क्रान्तेषु शरीरं श्वयितुम् अध्रियत ।
तस्य शरीर एव मन आसीत् ॥

so ’kāmayata -- bhūyasā yajñena bhūyo yajeyeti ।
so ’śrāmyat ।
sa tapo ’tapyata ।
tasya śrāntasya taptasya yaśo vīryam udakrāmat ।
prāṇā vai yaśo vīryam ।
tat prāṇeṣūtkrānteṣu śarīraṃ śvayitum adhriyata ।
tasya śarīra eva mana āsīt ॥

He desired to sacrifice again with a greater sacrifice. He toiled and performed penance. And while he toiled and performed penance, glorious power went out of him. Verily glorious power means the senses (prâna). Then when the senses had gone out, the body took to swelling (sva-yitum), and mind was in the body.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)