Having rolled done a mountain, a rock lies in a valley. -
Why did it fall? Nowadays no one knows -
Did it break off from the heights of its own accord,
Or was it hurled down by an external will?
Century after century has gone by:
Still no one has resolved this question!

Fyodor Ivanovich Tyutchev

http://www.poemhunter.com/poem/probl-me/