17: "The divine essence that, pervading the entire universe of millions of solar systems, is caught up by our sun and passed out in a manifested form to the utmost boundaries of our solar system, so that this manifested essence may be the basic soil of the growth, preservation and destruction of our worlds, that divine essence is simple Nadam of our yogic philosophy and that Nadam or OM subsequently manifests itself as seven streams.  The unmanifested is manifested by or borne by the subsequent ramifications.  These streams are the seven vowels or seven notes.  These seven vowels and notes must have special correlations with the seven vedic metres, since in the Vishnu Purana, Parasara describes the vedic metres as the coursers of the solar essence."—Some Thoughts on the Gita, p. 74.