How to do an optical illusion with a fushigi ball

I know this isn't all that earth shattering. But I thought it was kind of neat and decided to share. :)

The Fushigi ball is the acrylic ball with a metal ball inside it that you might have seen on TV. It's used for a form of juggling called Contact Juggling. It was pretty popular this past year.

So I figured some of you might have one and might like this optical illusion you can do with one. I discovered this last summer by accident.