J. Böhme, Theosophische Wercke, Amsterdam [1682] (Public Domain Image)

Clairvoyance by C. W. Leadbeater [1899]

This is a Theosophical manual of the phenomena of Clairvoyance, the mental viewing of things far removed in space and/or time. Leadbeater appeals to the fourth dimension, the Akashic record, and the assistance of unseen spirits, as explanations of the phenomena. Students of the occult will find this a satisfying review, but more rationalist minded investigators will find this more of a counter-example of how to research psi.