Atṭhika saññā bhāvanā is the contemplation on the parts of a skeleton. By practicing atṭhika saññā frequently, one may advance the meditation for the cessation of defilements. One develops passion, hatred, and delusion because of the unrestrained eye, which is attracted to the details of forms seen. The eye can be disciplined by practicing atṭhika saññā, which avoids the eye attracting to details of forms.
In ancient Sri Lanka, a Buddhist monk named Tissa was travelling on foot from Mihintale, a small town, to Anuradhapura, a big city, to venerate the Sri Mahā Bodhi tree, which was a sapling of the sacred Bodhi tree of India. The monk met a woman on the way when she was running away from her husband; she smiled at the monk and walked away. Her husband who followed the woman met with the monk and enquired whether the monk had seen a woman. The monk replied saying that “I saw a skeleton; did not know whether a man or a woman”. This incident, reported in the ancient writings, illustrates disciplining the eye by practicing atṭhika saññā.
One may improve the mind to eradicate defilements by practicing insight within the concentration developed through atṭhika saññā. In order to practice atṭhika saññā, one sits in front of a skeleton or a picture of a skeleton and focuses attention on the skeleton. By carefully observing the details of the skeleton, from head to toe, one develops a mental image of the skeleton. Once the image of the skeleton is well established in the mind, he or she contemplates on the skeleton while sitting at the same place or after moving to an appropriate location.