釋禪波羅蜜次第法門 3.23

3.23

Answer: These five places are convenient for applying the mind, whereas other places are not loci for tranquilizing it. Places such as the flanks and ribs are all off-center, so they are not mentioned. Just as the roundness of the head models heaven, and the squareness of the feet models earth, the navel is the ocean of qi, the nose is the gate of wind, and the hairline is the place for cultivating the contemplation of bones; therefore, they are taken as gates.