"This study of Raja-Yoga takes a long time and constant practice. A part of this practice is physical, but in the main it is mental. As we proceed we shall find how intimately the mind is connected with the body... If the body is sick, the mind becomes sick also. If the body is healthy, the mind remains healthy and strong. When one is angry, the mind becomes disturbed. Similarly when the mind is disturbed, the body also becomes disturbed. With the majority of mankind the mind is greatly under the control of the body, their mind being very little developed. The vast mass of humanity is very little removed from the animals. Not only so, but in many instances, the power of control in them is little higher than that of the lower animals. We have very little command of our minds. Therefore to bring that command about, to get that control over body and mind, we must take certain physical helps. When the body is sufficiently controlled, we can attempt the manipulation of the mind."

- Swami Vivekananda, "Introductory" (Dec 14, 1895, New York Vedanta Society), Raja-Yoga, Complete Works: Vol 1