from an article in The Mechanics’ magazine, Vol 12, No. 317, page 17, by Henry D—.
“We see therefore a material difference between the portraits by Rembrandt and those of Rubens; the former painted by the light of the small window of a mill, while the latter had light from nearly the whole side of the apartment. The plan most in vogue at the present day is to darken all the window, except the top row of panes, but this, at certain seasons, is attended with the disadvantage of darkening the room so much, as often to deprive the painter of a sufficiently clear light on his canvas. . . It represents an artist’s study, having two windows, between these there is a partition A, of wood or thick curtain, dividing the room into two separate apartments. In the partition . . . and about 4 feet from the floor, there is to be an opening C, of 3 or 4 feet square, through which the artists, standing in the room B, may see the person in D.” (page 17)