There's an old Irish method of cursing someone that involves water-rolled stones.
You extinguish your fire (or theirs) and build a pile of water-rolled stones in the hearth. You then place an eggshell filled with water on the top of the pile of stones and issue a curse that the target will have no luck until the 'Fire of Stones' (as the curse is known) boils the water in the eggshell.
You then take the stones and bury them over a wide area, making the task impossible for them.
Purely my speculation here - This could have origins in burnt mounds being found by early farmers.