Kindly observe your self in your daily life for few moments. You will find that you can not sit in any posture for more than few minutes without any movement. Even your most common posture you may keep on either moving your hand or head or eyes so on...even though you are healthy you can not still yourself and sick people have more difficulties in maintaining the stillness of body and mind with awareness.

The most difficult thing is to become still with ease in any posture for few moments with awareness and concentration. It is not a matter of only physical posture but also alignment of you body with your own mind. In our world most of the time our body is some where and mind is somewhere else. We need a high level of  awareness and concentration for perfection of a posture.

It is said that once there were 8.4million postures, which is related to 8.4million species. Each species whether it is merely a stone or a mountain or cow you can have one Asana resemble to that species.

Now a days there are 84 main postures which completely overhaul your muscular and nervous system.