Minecraft wiki entry for Pistons, associated text: Beta 1.7 - Beta 1.9 Prerelease: [Has no defined name, rendering a minimum-length text box if highlighted]
Beta 1.9 Prerelease 2 - Beta 1.9 Prerelease 3: [Has no defined name, and attempting to render it causes a game crash]
Beta 1.9 Prerelease 4 - 13w25b: [Has no defined name, rendering a minimum-length text box if highlighted]
13w25c - 13w36b: tile.null.name