I forgot the name of a trick which I would like to buy, it works somehow like this: Spectator thinks of a card and writes it down on a piece of paper. Performer reads his mind and knows card.

But the performer never gets hold of the piece of paper. The trick is somehow in the pen.

It was relatively inexpensive, between 10 and 15 dollars, I'd say. I have forgotten the name....was it "impossible"? HMH. Help would be appreciated. Thanks, Mark