The Unknown Guest by Maurice Maeterlinck, Supernatural, Ghost

I had hoped that a single volume would be able to contain the result of these investigations, which, I may say at once, will teach nothing to those who have been over the same ground and which have nothing to recommend them except their sincerity, their impartiality and a certain scrupulous accuracy. But, as I proceeded, I saw the field widening under my feet, so much so that I have been obliged to divide my work into two almost equal parts. The first is now published and is a brief study of veridical apparitions and hallucinations and haunted houses, or, if you will, the phantasms of the living and the dead; of those manifestations which have been oddly and not very appropriately described as "psychometric"; of the knowledge of the future: presentiments, omens, premonitions, precognitions and the rest; and lastly of the Elberfeld horses. . . .