So that the crew would not have to use CGI to "fake" the magical illusions seen, Norton received intensive training in sleight of hand and other stage magic techniques from British magician James Freedman and American magician Ricky Jay.
Although the story is fictional, some details are based on the life of Austrian Crown Prince Rudolf, only son of Emperor Franz Josef. The painting Eisenheim creates is an actual portrait of Franz Josef. The bodies of Rudolf and his mistress, the Baroness Mary Vetsera, were found at his hunting lodge, Mayerling, on January 30, 1889, in what became known as the "Mayerling Incident". The Imperial Family covered it up at first, creating controversy and mystery.
The Orange Tree trick was made famous by a 19th Century French magician named Robert-Houdin. It was from Robert-Houdin that another magician, Ehrich Weiss, came up with the stage name Houdini. This trick is first mentioned in old Indian manuscript as an illusion by Faux. Pinetti, an 18th century magician, did a similar trick, but he used lemons. Houdin was the first one to use real fruit.
The method for creating the ghosts as shown to inspector Uhl involved the projection of a pre-recorded image into a hazy background. Since the ghosts Eisenheim conjured could speak to and interact with the audience, he most likely used a different method popular among magicians at that time. A fantascope was used to illuminate a real person off stage. The image was reflected off of a mirror or glassplate, creating a ghosted image. The lanterns that Eisenheim tells his assistants to leave behind when they are packing up the workshop bear a strong resemblance to fantascopes.
When Sophie comes up on the stage during Eisenheim's show, she lifts the hem of her dress with one hand as she walks up the stairs. In the time this movie was set, a woman who lifted the hem of her dress with 2 hands was a prostitute.
When Inspector Uhl approaches Prince Leopold while hunting, to inform him of Eisenheim and Sophie's meetings, the Prince asks what they were seen doing together. The line asking if they were seen "fornicating" was originally filmed as "fucking." It was overdubbed to avoid an "R" Rating. MPAA policy stated that "fuck" could not be used to refer to intercourse in a PG-13 film.
When Eisenheim is performing at the Hofburg, he places the Crown Prince's sword upright on the stage. The first officer who attempts to lift it is unable. The second person to try, to whom the Crown Prince says "Not so eager, cousin", is also unable. That second person was probably meant to be Karl von Habsburg-Lothringen, who succeeded "Crown Prince Leopold's" father, Franz Josef, as Emperor in 1916.
When the Crown Prince was asking the Inspector if he saw Sophie and Eisenheim fornicating, the Prince's lips are clearly saying f***ing. The word fornicating was dubbed over so the movie could receive a PG-13 rating. Actors can use the f-word in a PG-13 movie if they are saying, for example, "I bumped my f***ing head!", but if the f-word is used in reference to sex, the movie will get an R rating.
The character Prince Leopold says during a performance of Eisenheim at the palace: "He tries to trick you ... I try to enlighten you. Which is the more noble pursuit?" This reference is to a famous slogan the RJ Reynolds tobacco company used in the 1930's that said "It's fun to be fooled ... it's more fun to know." The slogan was combined with adverts showing the secrets behind famous mysteries. The impetus for this was a tribute to the popularity of the American magician Horace Goldin.
The trivia items below may give away important plot points.
When inspector Uhl and his men are searching Eisenheim's workshop he picks up a glass bottle with a dark red liquid in it. This is the same bottle Eisenheim placed in the suitcase he gave to Sophie before her 'murder'. It contained the blood mixture used to fake the murder.
The original story on which the movie is based does not include the artifice of the protagonist framing the Duke for murder. The protagonist gets away with a serious crime and yet is made to seem justified in this film. However, it was stated earlier in the story that Leopold had actually killed another woman to cover up the fact he was abusing her. Also, he was planning to overthrow his father, the Emperor. This would have been considered high treason and was punishable by death, even if it were a member of the royal family. Therefore, Leopold did pay for his previous crimes, albeit in a roundabout manner.
Originally was conceived as an adaptation of Marvel Comics Doctor Strange, a master magician also known as Earth's Supreme Sorcerer. As the rights of the character were unavailable, the script was remade as a poorly version of the real magician Erik Jan Hanussen. In fact, Eisenheim have the same knob that Doctor Strange as a hidden nod for him. Eventually he was adapted in Doctor Strange (2016).