You will need 2 cups and a penny for this and some water.
1st you will need a big bowl filled with water
2nd then you take the 2 cups take one in each hand and put them together in the water
3rd you take it out of the water and put on a flat surface
4th you will need to hold both cups and stick the penny in the middle of the 2 cups and your done.
Congratulations You have finished the demo.
Here is a video to help if you still maybe don't understand =)