WHAT DELIGHT IN SEEING WHITE BONES?
Yanimani apatthani alapun' eva sarade
Kapotakani atthini tani disvana ka rati.
Like gourds cast away in autumn are these dovehued bones. What pleasure is there in looking at them? 
A group of monks went into a forest and practised meditation ardently and diligently and soon attained deep mental absorption (jhana) and they thought that they were free from sensual desires and, therefore, had attained Arahanthood. Actually, they were only overestimating themselves. Then, they went to the Buddha, with the intention of informing him about what they thought was their attainment of Arahanthood.
When they arrived at the outer gate of the monastery, the Buddha told Venerable Ananda, 'Those bhikkhus will not benefit much by coming to see me now. Ask them to go to the cemetery first and then come and see me.' Ananda then delivered the message to those bhikkhus, and they reflected, 'The Enlightened One knows everything; he must have some reasons for making us go to the cemetery first.' So they went to the cemetery.
There, when they saw decayingdead bodies*, they could look at them as just skeletons, and bones, but when they saw some fresh dead bodies, they realised, with horror, that they still had some sensual desires awakening in them. The Buddha saw them from his monastery and sent forth his radiance and exhorted, 'Bhikkhus! Seeing these dead bodies, is it proper for you to have any sensual desire in you?'
Perceiving the fleeting nature of all sensual pleasures, all those bhikkhus realised the Dhamma.
*Dead bodies are classified as (i) bloated(uddhumataka), (ii) discoloured(vinilaka), (iii) festering(vipubbaka), (iv) dissected(vicchiddaka), (v) gnawed-to-pieces(vikkhayitaka), (vi) scattered-in-pieces(vikkhittaka), (vii) mutilated and scattered-in-pieces(hata-vikkhittaka), (viii) bloody(lohitaka), (ix) worm-infested(pulavaka), and (x) skeleton(atthika).
During the time of the Buddha, these ten kinds of dead bodies were found in cemeteries and charnel places where dead bodies were not buried or cremated and where flesh-eating beasts and birds frequent. In modern days it is impossible to obtain such corpses as subjects for meditation.