In this meditation, you can sit or lie down. Then, without inwardly verbalizing the experience, you focus on some rhythmic occurrence within your body. An easy one would be to put your hands on your lower abdomen and focus on the sensation of your hands rising and falling with each breath. What is difficult is to avoid trying to control or modify one's breath while focusing on it.
OK, here is the quote about a variation on this technique from LeShan, back in groovier times:
One self-generated rhythm that has been used by some people is the pulse rate. This is observed either in the moving of an artery or the artery is palpated. I strongly recommend not doing this without the constant supervision of an experienced and medically trained teacher. It is very difficult in this one to avoid modifying your own pulse rate, and anyone who plays around with his own heartbeat is this fashion needs either a good psychiatrist or a certificate of entry into the nearest home for the feebleminded.OK, then! You have been warned.
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