I have read the book the book art of super realisation by Swami yogananda .My question is that is it necessary to get a armless chair and woolen blanket I only have acces to yoga mat is it ok if I can use that and what is the reason of doing it on a armless chair and woolen blanket on it .
The purpose of his instructions (regarding armless chair for meditation) is primarily to help those who cannot sit on the ground, especially westerners who are accustomed to sitting cross legged. Yognanda came to the West in 1920 and you can imagine that he could not have taught yoga floor positions without eliminating thousands of potential students. Besides, there’s a deeper truth: the only real essential point is the necessity of sitting upright, whether in a chair or on the floor. The position of the spine is the most important part of the asana of meditation.
The armless chair instruction relates to the position of the arms on the thighs with the hands open and point upwards. Arms on a chair would conflict with the position of the elbows.
So if you are more comfortable on the yoga mat what you will need to do is work on one of the three or so basic floor positions that will allow you to relax with an upright spine in order to meditate deeply. A good hatha teacher can assist you.
The blanket, wool, cotton, or silk, or, in former times, the skin of a deer or tiger, is there to provide subtle insulation from downward pulling currents of the earth. I won’t go into a complete explanation here but a simple and practical approach is to place a wool blanket down and cover with a piece of silk — if you can. Even just a cotton cloth is better than nothing. ok?
Blessings to you upon your meditations!