It has not been found possible to determine, before experiment, whether any given man or woman will prove capable of the hallucinatory experiences.
The evidence, of course, is necessarily only that of the scryers themselves, but repeated experiments by persons of probity, and unfamiliar with the topic, combined with the world-wide existence of the practice, prove that hallucinatory pictures are really induced.
It is useless to make experiments with hysterical and visionary people, "whose word no man relies on"; they may have the hallucinatory experiences, but they would say that they had in any case.
Persons of recognized "imaginativeness," such as novelists and artists, do not seem more or less capable of the hallucinatory experiences than their sober neighbours; while persons not otherwise recognizably "imaginative" (we could quote a singularly accurate historian) are capable of the experiences.
But hallucinatory figures, both in dreams and waking life, are not necessarily those of the living; from the reappearance of dead friends or enemies primitive man was inevitably led to the belief that there existed an incorporeal part of man which survived the dissolution of the body.
Pseudopremonitions, due to hallucinatory memory, are not unknown; there is also some ground for holding that crystal-gazers are able to perceive incidents which are happening at a distance from them.