The Discourse on Great Benefit
"The perception of a skeleton, monks, when developed and cultivated, leads to great benefit. And how, monks, is the perception of a skeleton developed, how is it cultivated, so that it leads to great benefit? Here, monks, a monk develops the enlightenment factor of mindfulness accompanied by the perception of a skeleton, etc. He develops the enlightenment factor of equanimity accompanied by the perception of a skeleton, based upon seclusion, based upon dispassion, based upon cessation, maturing in release. Thus developed, monks, the perception of a skeleton, thus cultivated, leads to great benefit."