But he was also a psychic investigator. While on tour he would make a point of exposing fake mediums, and, more systematically, he was appointed a member of a committee set up to look into the subject by the Scientific American. The committee, which was set up in January 1923, paid a visit to the home of a medium who called herself Margery. Here is a photograph of Houdini, Margery, Walter Franklin Prince, who ran the American Society of Psychical Research and Malcolm Bird, an assistant editor of the Scientific American.

Before the seance, Houdini had made some preparation and knew what he was looking for. He was to sit on the medium's left. Consequently, all that day he had worn a tight bandage just below the knee of his right leg, which had thus become swollen and tender. During the seance he rolled his right trouser leg up above his knee, so that with his sensitized leg he might feel any movement or flexing of Margery's leg against his.

Figure 2 Margery's husband carries the box with the bell in it into the seance room.

This preparation was especially directed at a manifestation which had hitherto baffled all the members of the committee. This involved an electric bell enclosed in a box, which would ring whenever a certain pressure was applied to the boards on top of the box. In previous seances, the bell had rung repeatedly when the box had been placed on the floor in front of Margery, even though the sitters were sure that they had perfect control over her hands and feet. The explanation she gave was that her dead brother Walter must have closed the circuit. He had not only rung the bell, but had used code to answer questions with it.

On this particular evening the box was placed between Houdini's feet, with his right foot between it and Margery's left foot as we see in these drawings from Houdini's notebook.
"As the seance progressed I could distinctly feel her ankle slowly and spasmodically sliding as it pressed against mine while she gained space to raise her foot off the floor and touch the top of the box. To the ordinary sense of touch the contact would seem the same while this was being done. At times she would say: 'Just press hard against my ankle so that you can see that my ankle is there,' as she pressed I could feel her gain another half inch. " -Harry Houdini-

When she had maneuvered her leg round into position where she could reach the bell, Houdini felt the tendons of her leg tighten whenever she touched the box. Then, when the ringing was finished, he could feel her leg slide back into its original position with her foot on the floor beside his own.

On Margery's right sat Bird, and beside him Margery's husband Dr. Crandon. Bird held Margery's right hand and the doctor's left hand in one of his, thus leaving his other hand free 'for exploring purposes'. Suddenly, Margery went into trance and spoke with the voice of her dead brother Walter, who had been killed in an accident on the railroad. His voice was gruff and deep pitched, and he asked for an illuminated plaque to be placed on the lid of the box containing the bell, and Bird went to get it.

Figure 3 Bird got up to get the luminous plaque

When the spirit Walter called for 'control', Margery immediately placed her right hand in Houdini's, suddenly the cabinet, which stood behind Margery, was thrown over violently. She then gave Houdini her right foot, too, saying, "You now have both hands and feet." Walter then called, "The megaphone is in the air. Have Houdini tell me where to throw it."

"Toward me," replied the magician, and it instantly fell at his feet. This manifestation also had taken place before, and Houdini said, 'it had converted all skeptics.'

Figure 4 The spirit voice of Walter calls out, "The megaphone is in the air!"