Galton, F. (1883). Mental imagery. In F. Galton, Inquiries into human faculty and its development (pp. 83-114). New York, NY, US: MacMillan Co.
http://dx.doi.org/10.1037/14178-016
Anecdotes find their way into print, from time to time, of persons whose visual memory is so clear and sharp as to present mental pictures that may be scrutinised with nearly as much ease and prolonged attention as if they were real objects. I became interested in the subject and made a rather extensive inquiry into the mode of visual presentation in different persons, so far as could be gathered from their respective statements. It seemed to me that the results might illustrate the essential differences between the mental operations of different men, that they might give some clue to the origin of visions, and that the course of the inquiry might reveal some previously unnoticed facts. It has done all this more or less, and I will explain the results in the present chapter. (PsycINFO Database Record (c) 2016 APA, all rights reserved)