The Yoga Siddhi said by Thirumoolar

Thirumoolar in his thirumanthiram's third thanthiram, in attaanga yoga, he has explained yoga in a simpler  way.

"பன்னிரண்டானைக்குப் பகல் இரவுள்ளது

pannirandaanaikkup pagal iravullathu

பன்னிரண்டானையைப் பாகன் அறிகிலன்

pannirandaanaiyaip paagan arikilan

பன்னிரண்டானையைப் பாகன் அறிந்தபின்

pannirandaanaiyaip paagan arinthapin

பன்னிரண்டானைக்குப் பகல் இரவில்லையே!

pannirandaanaikkup pagal iravillaiyae!"

- திருமந்திரம் (Thirumanthiram)

The sun, is the prana (life/oxygen) which acts for 12 inches, have day and night. The oxygen that goes from nose through throat and goes down and this is not known to the soul(life) that is in the head.

But if the oxygen goes to the top from down, the soul will definetely know about it. Like wise if the sun or the soul knows it, then the soul gets brightness irrespective of day and night.

Pannirandaanai:- The oxygen runs through the 12 inches.

Paagan arikilan:-  When the oxygen goes down towards the lungs, the soul does not know about it.

Paagan arinthapin:- When the oxygen goes towards head, the soul will know about it.

Pagal iravillaiye:-  There is no birth and death to the one who made oxygen go towards the head.

It is said that this way of taking the oxygen towards the head is said as Yoga Kalpa and also as Yoga Kaaya siddhi.

The siddhi that we attain by making the oxygen go towards the head is called the Yoga siddhi.

Hence while attaining yoga siddhi by means of yoga, one should not leave the yoga practices considering it as hard and should be determined of avoiding the re-birth by winning over the death. If they practice with such a determination then there is no doubt that Yoga Siddhi will be easily attained.