`Yagnavalkya,' he said, `how many Stotriya hymns will the Udgatri priest employ to-day at this sacrifice?' `Three,' replied Yagnavalkya. `And what are these three?' `Those which are called Puronuvakya, Yagya, and, thirdly, Sasya.' `And what are these with regard to the body (adhyatmam)?' `The Puronuvakya is Prana (up-breathing), the Yagya the Apana (down-breathing), the Sasya the Vyana (back-breathing).' `What does he gain by them?' `He gains the earth by the Puronuvakya, the sky by the Yagya, heaven by the Sasya.' After that Asvala held his peace.