If the limbs and sub-limbs of yama and niyama are to be practiced, steps should be taken to ensure that one does not fall victim to disease, obligation or poverty.
For when a person becomes ill, his mind cannot be steady, nor can he do any work. Therefore, the body, sense organs and mind must be stabilized to prevent obstacles, such as disease from occurring.
To bring the body and sense organs under control, the asanas (postures) should first be studied and practiced. Asana is the first step in the practice of the limbs of yoga.
It is not possible to practice the limbs and sub-limbs of yama and niyama when the body and sense organs are weak and haunted by obstacles. To destroy diseases of the body and sense organs, asana must be studied and practiced, which is why Swatmarama speaks of it as the limb to be undertaken first. From its practice, the body will be conditioned and this, in turn, will lead to improved health.
It is said that asana is primary, due to its being the first limb of hatha yoga. One should practice that asana which is a state of steadiness, freedom from sickness and lightness of body.
ha = the surya nadi
tha = the chandra nadi
The process of controlling the breath that moves through these two nadis is known as hatha yoga. Yoga means relation and strength. If the air we breathe throught the nostrils is governed by the rules and practice of pranayama, or breath control, the mind will be arrested:
the breath being in motion, the mind is moving. The breath being without motion, the mind must be motionless.
If our breath is moving and unregulated, the mind will be unsteady. Regulating the breathing stabilizes the mind and makes it firm. The methof for directing the stabilized mind toward the Inner Self is what is known as hatha yoga.