That body, in man, is again the heart within a man; for the pranas exist in it and do not go beyond.
Sama Veda, Chandogya Upanishad III, XII – Meditation on the Gayatri, 4
That Gayatri has four feet and is sixfold. The same is also declared by a Rik-verse:
Sama Veda, Chandogya Upanishad III, XII – Meditation on the Gayatri, 5
Such is its greatness (i.e. of Brahman as known through the symbol of the Gayatri). Greater than it is the Person (Brahman). One of Its feet covers all beings; the immortal three feet are in heaven (i.e. in Itself)
Sama Veda, Chandogya Upanishad III, XII – Meditation on the Gayatri, 6
The Brahman which has been thus described is the same as the physical akasa outside a person. The akasa which is outside a person is the same as that which is inside a person. The akasa which is inside a person is the akasa within the heart. The akasa which is within the heart is omnipresent and unchanging. He who knows this obtains full and unchanging prosperity.
Sama Veda, Chandogya Upanishad III, XII – Meditation on the Gayatri, 7-9
Of that heart there are five doors controlled by the devas. That which is the eastern door is the prana-that is the eye, that is Aditya (the Sun). One should meditate on that as brightness and the source of food. He who knows this becomes bright and an eater of food.
Sama Veda, Chandogya Upanishad III, XIII – Meditation on the Door-Keepers, 1
