For someone beginning with meditation, every aspect of the process raises a question. One of these questions relates to the body. The eventual goal is to attain a state whereby meditation can occur regardless of what the body is doing or how it is positioned. However, this is not usually the way things start out. Sri Aurobindo responds on this point.
The practice of Yoga Nidra is widely discussed in modern yoga circles. This involves attaining a lying-down posture for the body and then systematically relaxing all the limbs, muscles and calming the breathing, such that a state of deep relaxation and meditation can result. This practice frequently leads to a state of sleep, as the mind, the breath and the body all are habituated to treat such actions as an invitation to sleep.
If one attempts meditation while walking or standing, there is an increased level of alertness to the outer world, as well as physical reactions required to remain standing or moving, and these are habitually treated as an invitation to the consciousness moving outwards to the external world.
It is thus that the seated posture becomes the most recommended one for those starting with meditation. There are many recommendations for specific asanas to be attained, and specific ways of sitting to be followed, but the main issue for starting meditation should be a comfortable seated posture that can be held motionless for some time while the mind moves its focus inward or upward.
Eventually, as the practice of meditation deepens in the being, it can take place anywhere under any circumstances. The seeker, however, should be prepared for steps or stages to reach this result.
Sri Aurobindo writes: “The sitting motionless posture is the natural posture for concentrated meditation — walking and standing are active conditions. It is only when one has gained the enduring rest and passivity of the consciousness that it is easy to concentrate and receive when walking or doing anything. A fundamental passive condition of the consciousness gathered in itself is the proper poise for concentration and a seated gathered immobility in the body is the best position for that. It can be done also lying down, but that position is too passive, tending to be inert rather than gathered. This is the reason why yogis always sit in an asana. One can accustom oneself to meditate walking, standing, lying but sitting is the first natural position.”
Sri Aurobindo and the Mother, Growing Within: The Psychology of Inner Development, Chapter V Growth of Consciousness, Means and Methods, pg. 87