http://www.openculture.com/2019/03/new-archive-digitizes-80000-historic-watercolor-paintings.html

The watercolor painting has a reputation for lightness. It’s a casual endeavor, done in scenic outdoor surroundings on sunlit days. Watercolors are the choice of weekend hobbyists or children unready for messier materials. Watercolors, in other words, are often treated as unserious. But for a couple hundred years, they served a very serious purpose. In addition to being a portable medium with an expansive range, watercolors’ ease made them the primary means of making documentary images before photography completely took over this function by the turn of the 20th century when portable consumer cameras became a reality.