Touchstones are a type of block that appear in Super Mario 3D World and Captain Toad: Treasure Tracker. They can be touched with the Wii U GamePad which causes them to move to a set position until they are touched a second time which causes them to go back. In Super Mario 3D World they also return to their original position after a short time has passed. In their first appeareance in Super Mario 3D World only purple-colored Touchstones can be found in the levels Puffprod Peaks and Captain Toad Plays Peek-a-Boo making them very rare.
In Captain Toad: Treasure Tracker Touchstones can be found in various colors and shapes and are more common, their first appereance being the game's third level Touchstone Trouble.