[137] Furthermore, bhikkhus, a bhikkhu reflects upon this very body—however it is placed, however it is disposed—by way of the elements (dhātu): 'There are in this body the earth element, the water element, the fire element, the air element.' Just as, bhikkhus, a skilled cattle-butcher or a cattle-butcher's apprentice, having slaughtered a cow and divided it into portions, might sit at a crossroads of four great ways—even so, bhikkhus, a bhikkhu reflects upon this very body—however it is placed, however it is disposed—by way of the elements: 'There are in this body the earth element, the water element, the fire element, the air element.'
Thus he dwells contemplating the body in the body (kāyānupassanā) internally … In this way too, bhikkhus, a bhikkhu dwells contemplating the body in the body.
The Section on the Elements (dhātupabbaṃ).
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.