William Sidney Mount (1807-1868) devised an itinerant artists' wagon in 1852. He wrote: "A Design for an Artist waggon to sketch and paint in."
"During windy and rainy weather, no time is lost on account of the hot or cold air. This vehicle with glass windows can by drawn by hand, or behind a waggon if the painter should not wish to keep a horse. I believe the true painter should have no home," but should wander instead in search of subjects to paint.
(Thanks, Edward O'Brien.)