The Time Harry Houdini Tricked Teddy Roosevelt
In 1914, Teddy Roosevelt had been out of office for five years, and in June of that year was on a return journey from the Amazon. As an avid adventurer, this was, in his judgement, one of the last opportunities he'd have to explore such parts of the world (via History). While on the ship, Roosevelt was in the latter stages of recovery when he ran across the world-famous magician Harry Houdini. The former president was later in attendance when the latter performed a séance, a popular activity at the time.
The audience was instructed to write a question to be answered through his "connection" to nearby spirits (via Ozy). When Houdini correctly answered Roosevelt's question, the latter was amused by the apparent validity of the act. Yet Houdini was far from a believer in what he had just done (via Scientific American). While he performed the act with great skill, he saw the genre as deceptive and instead apparently chose to let Roosevelt know that.
Houdini's trick was dependent on careful planning and luck
In fairness to Teddy Roosevelt's skepticism, when meeting with Houdini the next day, he almost immediately asked whether the séance was a real connection to spirits or an elaborate trick. Per the account of Harold Kellock, Houdini verified it to be the latter (via Mental Floss). Upon learning that Roosevelt would be aboard the ship weeks earlier, Houdini spent time probing for information on Roosevelt's undisclosed travels the previous year. He even learned to forge the signature of W.T. Stead, who was a victim of the recent Titanic disaster and the spirit Houdini intended to have "answer" Roosevelt's question.
With the fake signature, a slate trick (whereby the answer Roosevelt wrote down was duplicated on one of two slates), and hope that Roosevelt would ask a question that corresponded with Houdini's pre-written answer of "Near the Andes" (the place Houdini learned that Roosevelt had spent the previous Christmas), the séance began. The end result was a gamble for which Houdini had a few contingency plans, as all these factors had to have the end result of it appearing as though W.T. Stead had written down where Roosevelt traveled to the previous year. The success of the trick apparently even surprised Houdini, who likely felt even more validated in his opposition to psychics.