One of the attractions of parapsychological research is that it is often necessary to abstain from a definitive judgement regarding certain phenomena. This also applies to physical mediumship. Although it can be assumed that the phenomena of most mediums have been produced by fraudulent means, this need not apply to all of them. Were there at least some mediums in the past whose phenomena were possibly genuine? The rich and diverse literature on physical media leaves this possibility open. It also contains a number of literature sources in various languages that are hardly known in an international context.

The study of these sources is fascinating and enlightening, also against the background of the questions of what control measures were used at the time and to what extent we can still learn from them today. As part of this historically oriented project, older sources were made available in English, which were originally only published in German, Italian, Polish, Portuguese and Hungarian.