Maitri (Maitrāyaṇīya) Upaniṣad 2.9

2.9

sa vā eṣa pañcadhātmānaṃ pravibhajya nihito guhāyāṃ manomayaḥ prāṇaśarīro bahurūpaḥ satyasaṃ kalpa ātmeti sa vā eṣo'sya hṛdantare tiṣṭhannakṛtārtho'manyatārthānasāni tatsvānīmāni bhittvoditaḥ pañcabhī raśmibhirviṣayānattīti buddhīndriyāṇi yānīmānyetānyasya raśmayaḥ karmendriyāṇyasya hayā rathaḥ śarīraṃ mano niyantā prakṛtimayosya pratodanena khalvīritaṃ paribhramatīdaṃ śarīraṃ cakramiva mṛte ca nedaṃ śarīraṃ cetanavatpratiṣṭhāpitaṃ pracodayitā caiṣo'syeti ||

'He, verily, having divided himself fivefold, is hidden away in secret—He who consists of mind, whose body is life (_prāṇa_), whose form is light, whose conception is truth, whose soul is space.'

[d] Verily, not having attained his purpose, He thought to himself from within the heart here: 'Let me enjoy objects.' Thence, having pierced these openings, He goes forth and 'enjoys objects with five reins.' These reins of his are the organs of perception. His steeds are the organs of action. The body is the chariot. The charioteer is the mind. The whip is made of one's character (prakṛti-maya). By Him forsooth driven, this body goes around and around, like the wheel [driven] by the potter. So, this body is set up in possession of consciousness; or, in other words, this very one is its driver.