Two examples of the use of a large sheet of plate glass.
1) A vertical coffin is set up on the stage. A member of the audience is invited to participate: s/he steps into the coffin and steps on to an adjustable platform in it, which is moved up or down so that the top of his/her head is at exactly the right height. S/he is then swathed with a sheet so that only his/her head is visible. The performer makes the appropriate gestures or invocations, and the person fades out to be replaced by a skeleton. The performer repeats the invocation backwards or reverses the sequence of the gestures and the skeleton disappears and the person is back.
2) A table with cloth is set up on the stage. Again, a member of the audience is invited up and seated to the left of the table (as seen from the audience). After appropriate spell-casting, a ghost appears and attempts to interact with the person: offer him/her a glass of wine, perhaps, or flirt, or (shudder) blow smoke in his/her face; but of course the person perceives nothing. At last, in disgust, the ghost gives up and disappears.
In both cases, the performer asks the person what the experience was like; naturally s/he reports that nothing happened, so it's only fair that someone else comes up and repeats the experience.
In both illusions, there's a sheet of plate glass (absolutely clean) placed diagonally in front of the coffin or table.
The figure illustrates how the first illusion is created. The coffin is illuminated by lights off to one side, which the audience can't see. The skeleton is suspended off to one side as shown; it's illustrated also by lights that the audience can't see, and of course the invited person can't see the skeleton due to the construction of the set. To begin with, the lights around the skeleton are dark, but to create the illusion they are brought up to full brilliance at the same time as the ones beside the coffin are darkened. As long as the total amount of illumination remains pretty well the same the audience won't perceive any difference; it the set is constructed properly the person in the coffin won't perceive much difference either. The skeleton is reflected onto the glass and completely obliterates sight of the person in the coffin.
The second illusion is similar, except that the scene off to the side (where the "ghosts" appear), is not separately illuminated; lights at the side of the set are turned up and the light level is sufficient to do the reflection. Again, because of the construction of the set, neither the audience or the person can see the "ghosts" and their actions.
In both illusions, the audience members will have to come up in to the stage on their right, so that they can be guided to the coffin or table without perceiving the sheet of glass. Care will also be needed in the construction of the set to ensure that the position of the skeleton or ghost is not visible as the volunteer comes on stage.
In the first illusion, some patter will have to be devised to cover the adjustment of the position of the head: perhaps something like making sure that all the audience can see things properly, or (risky) that the dead can only come through at a particular point in space; the real reason being that as long as the head of the person and the skull pretty closely coincide the illusion will work. Otherwise audience members will see both the head and the skull and that won't do. But it is permissible to change the appearance of the skeleton somewhat between the first and second volunteers.
Likewise, in the second illusion a second assistant can be used: perhaps the ghost can be of the other sex to the volunteer each time.
The original description of these illusions has them as part of a tour: a macabre cafe to begin with, where visitors sit at a coffin and have orders taken by an undertaker; the second and third rooms are the illusions described here. A person dressed in Charon's likeness originally conducted the volunteers to the coffin but these days some better-known personage must be employed. Mournful music and melancholy bells sound as the people proceed. But each of the illusions stand on their own feet and can be performed in isolation — but not in the same show.