Raja Yoga first brings about a quieting of the mind and a stilling of the body so that the advanced stages of deep trance or concentration may take place. While Hatha Yoga has a vast array of asanas and pranayama techniques, Raja Yoga, since it is focused on quieting the mental instrument, only adopts a very limited set of asanas and pranayama to avoid getting bogged down with all the physical techniques while providing the “firm seat” needed for its practices. The preliminary practices, called Yamas and Niyamas, establish various standpoints in relation to action in the world, such as ahimsa (non-harming), santosha (contentment) while establishing disciplines for avoidance of greed, jealousy, sexual focus and other forces which not only are distractions from the yogic practice, but which tend to disturb the needed quiet poise of the mental stuff, chitta. The prescriptions are not so much “moral” judgments as practical statements of an understanding of the way the mental substance reacts and vibrates to the impressions of the senses and the impulsions of the vital forces of desire.
As a result of this process of stilling the mental substance, the powers of concentration are enhanced and, as described by Patanjali, various powers of knowledge through identity with the object of concentration can arise. Eventually, the processes of Raja Yoga allow the practitioner to shut out the reactions and responses to the sense impressions, and the state of Samadhi, a deep state of concentrated trance, arises. There are various levels of Samadhi, including those called “with seed” and those “without seed”, indicating the level of completeness of detachment from the normal operation of the sense mind and the senses. Sri Aurobindo describes the result of Samadhi: “By Samadhi, in which the mind acquires the capacity of withdrawing from its limited waking activities into freer and higher states of consciousness, Rajayoga serves a double purpose. It compasses a pure mental action liberated from the confusions of the outer consciousness and passes thence to the higher supramental planes on which the individual soul enters into its true spiritual existence. But also it acquires the capacity of that free and concentrated energising of consciousness on its object which our philosophy asserts as the primary cosmic energy and the method of divine action upon the world. By this capacity the Yogin, already possessed of the highest supra-cosmic knowledge and experience in the state of trance, is able in the waking state to acquire directly whatever knowledge and exercise whatever mastery may be useful or necessary to his activities in the objective world. For the ancient system of Rajayoga aimed not only at Swarajya, self-rule or subjective empire, the entire control by the subjective consciousness of all the states and activities proper to its own domain, but included Samrajya as well, outward empire, the control by the subjective consciousness of its outer activities and environment.”
Sri Aurobindo, The Synthesis of Yoga, Introduction: The Conditions of the Synthesis, Chapter 4, The Systems of Yoga, pp. 31-32