From which of his limbs does Fire shine forth? From which of his limbs issues the Wind? Which limb does the moon take for measuring rod when it measures the form of the great Support?

Atharva Veda X, 7, 2

In which of his limbs does the earth abide? In which of his limbs the atmosphere? In which of his limbs is the sky affixed? In which of his limbs the great Beyond?

Atharva Veda X, 7, 3

Now, verily, that which is the Udgitha is the Pranava; that which is the Pranava is the Udgitha. Yonder sun is the Udgitha. It is the Pranava, because it moves along uttering Om.

Sama Veda, Chandogya Upanishad I, V - Meditation on Om as the Sun and the Prana, 1

Kaushitaki in olden times said to his son: I sang the praise of the sun regarding it as one with its rays; therefore you are my only son. Meditate on the rays and the sun as different from each another and you will have many sons. So much with reference to the gods.

Sama Veda, Chandogya Upanishad I, V - Meditation on Om as the Sun and the Prana, 2

Now with reference to the body: One should meditate on the Udgitha as the principal prana, for (i.e. the prana) moves in the body uttering Om.

Sama Veda, Chandogya Upanishad I, V - Meditation on Om as the Sun and the Prana, 3