Factual error: When Eisenheim is at the Vienna rail station, catching his train after the Crown Prince has died, the overhead electric cables of the modern railway are visible in several shots.
Factual error: When the narrator says Eiseinheim bought a theater, watch the houses on the background, on the right side of the screen. One of them has a visible modern antenna on its roof.
Answer: The trick is done with electromagnets under the stage holding the sword upright and stuck to the floor (switched off when Leopold takes the sword). Audiences at the time would have been unfamiliar with such a technique.
Sierra1 ★