The source I had, involved Randi carefully not telling us how he did the trick, so in the book I speculate how he might have done it. In the trick, Walters draws a picture and seals it up. Randi concentrates, then appears to draw on a pad, then puts his pen down. Walters opens up her envelope and shows it to the camera. Randi then, almost immediately shows a similar drawing. Here's what I said:
What we see when watching the show is Randi apparently drawing his copy of the picture on a pad using a ball pen, before Walters reveals her picture. It is possible, even using the technique I’m going to suggest, that Randi did do a little drawing at that point in the proceedings – if so, what he produced was probably a basic box, which he could adapt later for whatever was needed. It’s equally possible that he didn’t draw anything, but merely moved the pen to make it look as if he was putting something on paper.
When Walters shows her picture to the camera, and all eyes are on the image, Randi is holding his pad in front of him, with the writing surface facing towards his body. He isn’t holding the pen, so he can’t be drawing anything, right? Except there is an old magician’s trick of fixing a pencil lead under the fingernail, and using that to draw something unseen, concealed behind the pad. The same thing can be done with the end cut off a ball pen refill. What you get, in effect, is a finger end that draws like a pen.
This is, I’m convinced, is how Randi performed the trick, adding in details to the image while Walters was displaying her picture to the camera. He couldn’t look at his own picture much as he did so or it would have given the game away – and this would explain why his stick figure ended up on top of (or as he put it “in”) the house rather than alongside it. The clues that Randi may have given when he described what happened are that he made a big thing at the time of adding the sun to make the picture more like the original – emphasizing, perhaps how he worked by adding drawings after the event – and also he would later stress in a video where he discusses the event, that he used a ball pen where Geller used a big marker pen which would be harder to duplicate with this technique (in fact, Geller drew his image in plain sight, so couldn’t use this technique).
Take a look and see what you think.
Yesterday, though, I received an email from an Italian reader. Apparently Randi had admitted on Italian TV how he did this, and it wasn't with a fingertip pen. It seems he used his belt buckle - and certainly, just before the camera pulls away from Randi and onto Walters showing her image, his pad is moving very close to his belt. Even if it wasn't prepared, some metals will leave a coloured marking on paper, and I'm guessing that this is what my Italian correspondent (himself suitably magically mysterious) was suggesting.