Found on the South Australia Medical Heritage website.  Attributed to an article in the Journal of Clinical Investigations, vol 49, Issue 6 (June 1, 1970), pg 1238.  Described as:

“The picture above shows a schematic design of one of DuBois’ early plethysmograph designs from the early 1950’s. The person sat inside a large box filled with warm water, which would allow for easy monitoring of volume changes. It is reported that as the person entered or left the box, it flooded the Dean’s office below. For some strange reason, this design did not last long.