Saw this here.
1765
Perspective apparatus designed by the engineer James Watt and made by him in Glasgow in 1765. This is an ingenious device, easily transportable, for use in external perspectives. The apparatus folds away into a fitted hardwood case, which also forms the drawing board; its stand fits together to form a walking stick. Science Museum, London.
Drawing Instruments 1580-1980, Hambly M, 1988
