Chandogya Upanishad 6.7.6

6.7.6

evaṃ somya te ṣoḍaśānāṃ kalānām ekā kalā atiśiṣṭābhūt \
sānnenopasamāhitā prājvālī \
tayaitarhi vedān anubhavasi \
annamayaṃ hi somya manaḥ \
āpomayaḥ prāṇaḥ \
tejomayī vāg iti \
tad dhāsya vijajñāv iti vijajñāv iti \\607.6\

5. ‘Just as, my dear, one may, by covering it with straw, make a single coal of the size of a fire-fly that has been left over from a great kindled fire blaze up, and with it the fire would thereafter burn much— so, my dear, of your sixteen parts a single sixteenth part has been left over. After having been covered with food, it has blazed up. With it you now apprehend the Vedas; for, my dear, the mind consists of food, the breath consists of water, the voice consists of heat.’ Then he understood from him—yea, he understood.