I think I think
Therefore I think I am
Never did anything with crystals, but you can have fun with a pendulum. Try this simple experiment: Make a makeshift pendulum (small weighto n a bit of string - a clip on a diving reel would probably work
) and draw a thick black line on a piece of paper.
Hold the pendulum above the line. Then, stare at the line intently.
Hey presto, the pendulum will start to swing along the line!
WWWwwwwooooOOOooooOOO!