‘In the zazen of patch-robed monks, first you should sit correctly with upright postture. Then regulate your breath and settle your mind…
In the Mahayana there is… a method for regulating breath, which is knowing that one breath is long, another breath is short. The breath reaches the tanden and comes up from the tanden. Although exhale and inhale differ, both of them occur depending on the tanden. Impermanence is easy to clarify, and regulating the mind is easy to accomplish.
My late teacher Tiantong said, “Breath enters and reaches the tanden, and yet there is no place from which it comes. Therefore is is neither long nor short. Breath emerges from the tanden, and yet there is nowhere it goes. Therefore it is neither short nor long.”
My late teacher said it like that. Suppose someone were to ask Eihei, “Master, how do you regulate your breath?”
I would simply say to him: Although it is not the great vehicle [Mahayana], it differs from the lesser vehicle. Although it is not the lesser vehicle, it differs from the great vehicle.
Suppose that person inquired again, “Ultimately, what is it?
I would say to him: Exhale and inhale are neither long nor short.’ (Extensive Record, 390)