The original of YOGA considered as written by Maharshi Patanjali. He establish the astanga Yoga, eight sopan of Yoga, where as he didnot mention any yogasana, there is only two sloka in patanjali which discribre the Aasana Sutra 46 & 47. "Sthira Sukhasanam", "Prasatnashathilayanantsamapattibhyama".
Where as very few Aasana close to this definition. Later on the most ancient & scientific discription of Aasana was given in "dheranda Sanhita" and "Shiv sanhita".
With the passage of time many people had contributed a lot in this and developed so many new & revised form of aasana.
To enrich this more I have developed a new form of Yoga by the churning of YOGA and HASYA, it is HASYAYOGA. there are six sopan of this ;- Aachman, Aachran, Hasayasan, samvardhan, Dhyan and Maun. This is besically a esieast form of yoga, a stress bursting technique to rejounivate people. This give the benefit of Yoga asa well as laughter. The energy source of m-a-n. You may visit at http://www.hasyayoga.in
for more details.