L'Optique (The Optical Viewer). Dated: c. 1793. Dimensions: plate: 67.5 x 53.5 cm (26 9/16 x 21 1/16 in.) sheet: 70.3 x 57.4 cm (27 11/16 x 22 5/8 in.). Medium: etching and wash manner, printed in black. Museum: National Gallery of Art, Washington DC