Journal Article1894
Proceedings of the Society for Psychical Research, Volume 10 (incl. Report on the Census of Hallucinations)
Henry Sidgwick, Alice Johnson
Volume 10 of the SPR Proceedings (1894) contains the landmark "Report on the Census of Hallucinations" — the largest systematic survey of anomalous perceptual experiences undertaken in the nineteenth century. Over 17,000 people were asked whether they had ever had a vivid hallucination while awake; roughly 10% reported at least one such experience.