It was built from a standard cabinet with a hole cut in the door for the lens, a mirror positioned at 45 degrees inside and frosted perspex on the top onto which the light was focussed. Participants sat in front of it and leaned into a light-proof cloak on the top, seeing an image of the scene in front of them. They could then place tracing paper over it and copy the image.
The device worked but unfortunately the lighting in the room was not very bright so the image was pretty dim. It would have worked much better outside, of course!