The preliminary movement of Rajayoga is a careful self-discipline by which good habits of mind are substituted for the lawless movements that indulge the lower nervous being. By the practice of truth, by renunciation of all forms of egoistic seeking, by abstention from injury to others, by purity, by constant meditation and inclination to the divine Purusha who is the true lord of the mental kingdom, a pure, glad, clear state of mind and heart is established.
This is the first step only. Afterwards, the ordinary activities of the mind and sense must be entirely quieted in order that the soul may be free to ascend to higher states of consciousness and acquire the foundation for a perfect freedom and self-mastery. But Rajayoga does not forget that the disabilities of the ordinary mind proceed largely from its subjection to the reactions of the nervous system and the body. It adopts therefore from the Hathayogic system its devices of asana and pranayama, but reduces their multiple and elaborate forms in each case to one simplest and most directly effective process sufficient for its own immediate object. Thus it gets rid of the Hathayogic complexity and cumbrousness while it utilises the swift and powerful efficacy of its methods for the control of the body and the vital functions and for the awakening of that internal dynamism, full of a latent supernormal faculty, typified in Yogic terminology by the kundalini, the coiled and sleeping serpent of Energy within. This done, the system proceeds to the perfect quieting of the restless mind and its elevation to a higher plane through concentration of mental force by the successive stages which lead to the utmost inner concentration or ingathered state of the consciousness which is called Samadhi.
CWSA 23: 36