摩訶止觀 9.64

9.64

二、內無色以不淨心觀外色者：骨人是精血所成，應須呵滅，析骨四微。大乘體法，知骨從心生，心如幻化，骨人虛假，骨人自滅。如好馬任人意，如好人共事去來無捩。骨人去已，新法未來，喜多退墮。以不淨心但觀外色。外色者，外死屍等；又外者，骨人所放八色也。所以觀外色者，此去欲界猶近，須觀外不淨。若修壞骨人，別有觀法，今但論法發。忽見骨人自然消磨，但有八色及外不淨在。骨人滅時，位在中間。又見八色與內淨法同時俱起，青、黃等光更作一番增明。內淨、喜、樂、一心，四支功德轉勝於前，是為二背捨，位在二禪。

Second, the contemplation of external forms with a mind free of internal perceptions of form by observing impurity: The skeleton is formed of semen and blood; one must scold and extinguish it, analyzing the skeleton into the four minute elements. In the Mahāyāna bodily realization of phenomena, one knows that the bones arise from the mind; the mind is like an illusion, and the skeleton is provisional and unreal, so the skeleton naturally dissolves away. It is like a good horse yielding to a person's will, or like working with a good person where coming and going occur without friction. Once the skeleton is gone and new states have not yet arrived, regression frequently occurs. With a mind observing impurity, one only contemplates external forms. 'External forms' refers to external corpses and the like; furthermore, 'external' refers to the eight colors emitted by the skeleton. The reason one contemplates external forms is that one is still close to the desire realm, so one must contemplate external impurity. If one practices destroying the skeleton, there is a separate method of contemplation; here we only discuss the manifestation of phenomena. Suddenly one sees the skeleton naturally wear away and vanish, leaving only the eight colors and external impurity. When the skeleton vanishes, one's level is in the intermediate dhyāna. One also sees the eight colors arise simultaneously with internal purity, and the blue, yellow, and other lights once again intensify in brilliance. The virtues of the four factors—internal purity, joy, bliss, and one-pointedness of mind—surpass those of the preceding stage. This is the second liberation (vimokṣa), situated at the level of the second dhyāna.