The next step is Asana, posture. A series of exercises, physical and mental, is to be gone through every day, until certain higher states are reached. Therefore it is quite necessary that we should find a posture in which we can remain long. That posture which is the easiest for one should be the one chosen. For thinking, a certain posture may be very easy for one man, while to another it may be very difficult. We will find later on that during the study of these psychological matters a good deal of activity goes on in the body. Nerve currents will have to be displaced and given a new channel. New sorts of vibrations will begin, the whole constitution will be remodelled as it were. But the main part of the activity will lie along the spinal column, so that the one thing necessary for the posture is to hold the spinal column free, sitting erect, holding the three parts — the chest, neck, and head — in a straight line. Let the whole weight of the body be supported by the ribs, and then you have an easy natural posture with the spine straight. You will easily see that you cannot think very high thoughts with the chest in. This portion of the Yoga is a little similar to the Hatha-Yoga which deals entirely with the physical body, its aim being to make the physical body very strong.