Siva is considered to be the Adhi Yogi, First Yogi. He gave the world Vaasi Yoga. Vaasi Yoga is different from The Asthtanga Yoga of Patanjali in that while Vaasi Yoga directly reaches out to Consciousness, Asthtanga Yoga reaches out to Consciousness through the Modifications of Chitta. That is the cessation of thought processes.
Though it appears that we breathe through both nostrils, if we observe our Breath, we will notice that quantity of Air/Breath that pass through is not the same for both nostrils, Left and Right. Sometimes, breath passes more through the left nostril and at other times through the right nostril. The Left nostril belongs to / (called as) Moon and Right to Sun. When one holds the Breath, Sushumna, that holding of Breath belongs to or called as Agni, Fire. We shall see in detail in the forthcoming articles.
Matra is the time for taken for one involuntary wink.Tamil language is designed on Matra. Each letter of Tamil is assigned the time, Matra. For Instance A,அ is one Matra, Kuril,குறில்.) Aa ஆ has two Matras.The pronounciation of Siva Siva is assigned Four Matras. So for Puraka one has to chant mentally Siva Siva four times: Kumbhaka Siva Siva sixteen times