Even though Houdini explained that his feats were based on illusion and trickery, Doyle was convinced that Houdini had supernatural powers and said as much in his work The Edge of the Unknown. Houdini's friend Bernard M. L. Ernst recounted a time when Houdini had performed an impressive trick at his home in Doyle's presence. Houdini had assured Doyle that the trick was pure illusion and had expressed the hope that this demonstration would persuade Doyle not to go around "endorsing phenomena" simply because he could think of no explanation for what he had seen other than supernatural power.