Without support for feet or hands, sit only on the buttocks. Suddenly, the centering. Close your eyes. Feel the buttocks touching the ground. And because the buttocks have become sensitive, you will feel that one buttock is touching more. You are leaning on one buttock, and the other is touching less. Then move the leaning to the other. Immediately move to the other; then come to the first. Go on moving from one to the other, and then by and by, balance.
Once both your buttocks are balanced, suddenly you will be thrown to your navel center, and you will be centered inside. You will forget the buttocks, you will forget the body. You will be thrown to the inner center.