We don't know where it originally came from. It was described in a book from early 1920s, and that book referenced a book from the 1800s, which we have not seen.
A seminar student showed us a Navy manual from 1955, or there abouts, that alluded to the process.
Richard Welch, of Subliminal Dynamics, told of a book from the late 50s or early 60s that described it. (But he also said he invented it, but it is clear that he did not invent it. It is clear that he developed it.)
Paul didn't invent "mentally photographing" pages either. But he did develop the process, which is different from Welch's process.
Paul and our other associates (such as Patricia Danielson and Mike Bennett) developed and enhanced our activation techniques through the years. These activation techniques are invaluable for beginning PhotoReaders to develop conscious comprehension.
Learn it from where you think you will get the best instruction and the best support.