Ubasute

Ubasute (姥捨, abandoning an old woman?) (also called "obasute" and sometimes "oyasute") refers to the custom allegedly performed in Japan in the distant past, whereby an infirm or elderly relative was carried to a mountain, or some other remote, desolate place, and left there to die, either by dehydration, starvation, or exposure. It "is the subject of legend, but [...] does not seem ever to have been a common custom".[1] The practice was most common during times of drought and famine, and was sometimes mandated by feudal officials.

Ubasute has left its mark on Japanese folklore, where it forms the basis of many legends, poems, and koans. In one Buddhist allegory, a son carries his mother up a mountain on his back. During the journey, she stretches out her arms, catching the twigs and scattering them in their wake, so that her son will be able to find the way home.

From: http://en.wikipedia.org/wiki/Ubasuteyama