CHĀNDOGYA UPANISHAD · 3.13.8

तस्यैषा दृष्टिर् यत्रैतद् अस्मिञ् छरीरे संस्पर्शेनोष्णिमानं विजानाति ।
तस्यैषा श्रुतिर् यत्रैतत् कर्णाव् अपिगृह्य निनदम् इव नदथुर् इवाग्नेर् इव ज्वलत उपशृनोति ।
तद् एतद् दृष्टं च श्रुतं चेत्य् उपासीत ।
चक्षुष्यः श्रुतो भवति य एवं वेद य एवं वेद ॥

tasyaiṣā dṛṣṭir yatraitad asmiñ charīre saṃsparśenoṣṇimānaṃ vijānāti ।
tasyaiṣā śrutir yatraitat karṇāv apigṛhya ninadam iva nadathur ivāgner iva jvalata upaśṛnoti ।
tad etad dṛṣṭaṃ ca śrutaṃ cety upāsīta ।
cakṣuṣyaḥ śruto bhavati ya evaṃ veda ya evaṃ veda ॥

Namely, when we thus perceive by touch the warmth here in the body. And of it we have this audible proof: Namely, when we thus, after stopping our ears, listen to what is like the rolling of a carriage, or the bellowing of an ox, or the sound of a burning fire (within the ears). Let a man meditate on this as the (Brahman) which is seen and heard. He, who knows this, becomes conspicuous and celebrated, yea, he becomes celebrated.

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)