Asana is regarded as the first part of Hatha yoga.According to the Hatha yoga Pradipika (1: 17). ''Having done asana,one attains steadiness of body and mind,freedom from disease and lightness of the limbs.''
Asana literally means to be in a state in which you can remain physically and mentally steady and remain calm, quiet and comfortable.In the Yoga Sutras of Patanjali, the consise definition of yogasanas is''Sthiram sukham aasanam'' meaning that position that is comfortable and steady, and in this context they were practiced in order to enable the aspirant to be able to sit comfortably in one position for a very long time in order to meditate.
In hatha yoga this means something more,asanas refer to specific body positions which open the energy channels and the psychic centres.The ancient yogis discovered that the yogasanas became tools to higher awareness that they could develop,which enabled them to control the mind and energy.They also discovered that by developing control of the body through asanas,the mind could also be controlled.Therefore in the hatha yoga texts, asana practice always comes first.
In the yogic scriptures there are said to be 8,400,00 asanas, which represents the amount of different incarnations each individuals must pass through before attaining liberation from the cycle of birth and death.These asanas represented evolution from the simplest life forms of life to the most complex a fully realised human being.Through the ages the yogis have reviewed and modified them to the few hundred we know and practice today.