Visible crew/equipment: Near the beginning of the movie, the old priest is in Northern Iraq and you can see the shadow of a microphone on his hat.

The Exorcist (1973)
Plot summary
Directed by: William Friedkin
Starring: Ellen Burstyn, Jason Miller, Lee J. Cobb, Linda Blair, Max von Sydow
When Chris McNeil begins to notice strange things going on with her daughter, Regan, she takes her to the hospital. However, the doctors can't find anything wrong with Regan. Finally, believing that Regan is possessed by a demon, Mrs. MacNeil asks a priest who used to be psychiatrist, Damien Karras, to exorcise the demon.
Demon: I'm not Regan.
Father Damien Karras: Well, then let's introduce ourselves. I'm Damien Karras.
Demon: And I'm the Devil. Now kindly undo these straps.
Father Damien Karras: If you're the Devil, why not make the straps disappear?
Demon: That's much too vulgar a display of power, Karras.
Trivia: In the scene where Regan's mother is supernaturally blasted away from the bedside, she is being yanked by the crew by a length of rope. After dozens of takes director William Friedkin was still unhappy with the look of the shot and ordered the crew to haul her more fiercely. The scream in the shot that made the cut was of genuine pain and required no dubbing for effect.
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Answer: It was the demon moving objects around. This is seen later as well when object in Regan's bedroom are manipulated.
wizard_of_gore
Why doesn't the mother freak out when Regan is showing how to use the ouija board and the planchette moves into Regans hands by itself? It magically slides across the board into Regans hands by itself, and the mother isn't particularly startled by it? Doesn't make sense to me.
The movement of the planchette was so fast during Regan's insistence that it can be operated by one person that her mother thought Regan "must" have somehow done it.
Erik M.