As a punishment for his crimes, Hades made Sisyphus roll a huge boulder endlessly up a steep hill in Hell. The maddening nature of the punishment was reserved for Sisyphus due to his hubristic belief that his cleverness surpassed that of Zeus himself. Hades accordingly displayed his own cleverness by enchanting the boulder into rolling away from Sisyphus before he reached the top which ended up consigning Sisyphus to an eternity of useless efforts and unending frustration. Thus, pointless or interminable activities are sometimes described as “Sisyphean.” –Wikipedia

All people are like this when they are dead. The sinews no longer hold the flesh and bones together; these perish in the fierceness of consuming fire as soon as life has left the body, and the soul flits away as though it were a dream.    –Homer, Odyssey 11.4.4

And I saw Sisyphus at his endless task raising his prodigious stone with both his hands. With hands and feet he tried to roll it up to the top of the hill, but always, just before he could roll it over onto the other side, its weight would be too much for him, and the pitiless stone would come thundering down again onto the plain. Then he would begin trying to push it uphill again, and the sweat ran off him and the steam rose after him.  –Homer, Odyssey 11.13.4