In The Yogic World
In the yogic world, hatha yoga has its own importance.
The postures of hatha yoga are a form of physical action, yet they lead to detachment from physical action. Outer movements are taking place, of course -- the physical body is becoming stronger and more supple -- yet the whole purpose of hatha yoga is to draw the attention inward.
As you move the body with every breath, as you still the body with every breath, you bring it into perfect alignment. The fruit of hatha yoga is pratyahara, the withdrawal of the senses from outward attention...
Hatha yoga is really the best example of the principle of detachment in physical action. When it is achieved, the experience is so liberating; the physical body is no longer an impediment to sadhana (spiritual practice), no longer an obstacle. Your entire body and all its movements are a joyful expression of the spirit.
You can actually experience a great joy from each physical action. And in each action, you are aware of silence. In each hatha yoga movement, there is an air of silence, a pool of silence.
The Yoga of Discipline p. 165-166