Insta Square by Martin Lewis

I love Magic Squares but always thought of them as being a demonstration of mathematical skills rather than magic. Not that there's anything wrong with a demonstration of skill, I like having a variety of items in my show. But in this case, my goal was to make the Magic Square trick seem magical rather than mathematical.

This is Instasquare. You show a blank grid, drawn on your pocket notepad, and ask someone to call out a number. A wave of a pen and the grid visibly fills with random numbers. You then tear off the sheet, sign and date it, and give it to the stunned spectator, showing them sixteen different ways the Magic Square adds up to their chosen number. A memorable magic souvenir.