Johann Esaias Nilson, ‘Project d'une Grotte (Plan for a Grotto)’, ca. 1755/1760, National Gallery of Art, Washington, D.C.
plate: 26.7 x 19.9 cm (10 1/2 x 7 13/16 in.)  sheet: 40.3 x 25 cm (15 7/8 x 9 13/16 in.)