Yoga philosophy, is mainly based in the Sankya philosophy.
It is also said : Sankyans are nireshwara yogis and Yogis are seshwara sankyans. (nireeshwara – without god, seshwara – with god).
With the addition of God, some accept 26 tatwas in Yoga. But, for others, since, Ishwara is vishesha (special) purusha, it is still 25 tattwas.
For the state of knowledge which is said in the sankya, the practice is said here.
There are many, who teach yoga asana in the name of Sri Patanjali. But Sri Patanjali maharishi though supports asana,
specifies in one sutra “stiram sukham asanam”, and not the one which we see.
Though, there is Pramana for these asanas in books like Hatayoga pradipika etc.
The ultimate goal of yoga is samadhi. This is not some attainment, being established in ones own self is this samadhi
(tatra drshtu swaroope avastaanam).
The tradition of yoga was started by Hirangarbha – the creator.
The pramanika text on Yoga as philosophy is Yoga Sutra by maharishi Patanjali.
There are many commentories for this. The famous one being the bhashya of Sri Vyasa.This is commented upon by many. The famous being : Bhoja raja who has written a vritti, Sri Vijnana bikshus commentory and Sri Vachaspati mishras tatwa vaisharadhi.They in some place differ from the Bhashyakara Vyasa, and give some insight (different view) into the sutra.
For Book on Sutra with Sri Vyasa commentory (Tamil) see: Books -> Yoga
For Lectures : Lectures -> Yoga
For related Video visit : http://www.youtube.com/user/Shastralayam#p/u