It's a reference to Murnau's "Nosferatu" where a letter from Orlok is written in a strange ideographic language that includes a picture of a house, evidently relating Orlok's request to buy a house.
>somehow turn an intellectually handicapped gardener into a psychic genius
waddya mean somehow? They got him to understand the Sacred Geometry. I saw it in San Francisco when it came out and the guy next to me said "oh shit! it's the SACRED GEOMETRY!"