http://en.wikipedia.org/wiki/Rocking_stone

I found this looking elsewhere for rocking stones, if it helps. Cradle stone at Burghhead seems to be a different sort of thing, at least.

A grave slab with a hollowed surface called the Cradle Stone is built into the wall of the old graveyard at the top of Burghead. According to legend if you strike the stone in the hollow, the sound of a baby crying and a cradle rocking will be heard.