You display a small block with a picture of Houdini on it and place it in a clear tube.
You then pour water into the tube, until Houdini is totally submerged under water and cap the tube. The image of Houdini is clearly visible in the tube. You then cover the tube with a borrowed handkerchief.
After a few magic words the handkerchief is removed and Houdini has magically disappeared! He then appears from inside your pocket or inside a Top Hat or any place you desire.
The Apparatus stands roughly 12 inches high and can be seen by a fairly large audience