River Landscape with Sailboats

Aelbert Cuyp · ca. 1640–42 · Black chalk and gray, yellow, and grayish green wash; traces of a colorless varnishlike substance (probably gum arabic) on the grayish green wash toward the right; brown framing lines at the top and bottom and dark brown framing lines at the sides.

From the collection of The Metropolitan Museum of Art. Free to download, adapt and use — no permission needed.