Try this series of illusions all based on touch.
You will feel that the finger that was in the warm water feels cold and the finger originally in the fridge-cold water now feels warm, even though they are both now in the same temperature water. What's happened here is that when your finger was, say, in the warm water it adapted to that temperature. Your body is really only interested in things that change in the environment, as it is the changes that you need to be able to react to. So, after your finger has adapted to the warm water when it goes into the middle glass it's 'expecting' it to be warm. When it's not your brain reasons, "this isn't warm so it must be cold". Similarly, the finger in the fridge water adapts to coldness, and when it moves into the centre glass, that's not cold so it must be hot. So one finger is saying hot the other is saying cold and both are actually at the same temperature.
It will feel as though there are two marbles
It feels different to each hand. Why? Because the hand rubbing the fine sandpaper first adapts to feeling fine roughness, whereas the hand on the course sandpaper adapts to lots of roughness. So like the temperature illusion when your two hands have had their touch sensors adapted to different roughness, the medium paper will feel different to each.
You will feel a mysterious force lifting your arms - you may even find your hands rise all by themselves