I don't think that anyone of you has ever heared of any rock saling on its own without  the human help. I am sure that most of you have no idea about the Sailing Stone in Death Valley, California. 

Since 1915, the sailing stone has been a mystery when people saw a track with indicated a stone has moved in a dry land.
This sailing stone has been listed and studied more so that people can attain knowledge about their mysterious travel. Some believed that the rocks move due to the formation of the ice around the stone which makes them move while other still believed it is a mystery. No one can ever see those rocks moving. Some rocks take horizontal moments while other creates oval turns.

Well, It is still kind of a mystery.