OK, so speed isn't necessarily the most important thing in art, but this is an example of a painting done in under two minutes on a moving bus.
In the late 80's I was on a bus tour of England, Ireland, Scotland and Wales with Margaret, Evan and my parents. I constantly found myself observing beautiful landscapes through the window of the moving bus. So I set up my little sketch book, a 4 x 5 inch mini, and my watercolors, and after looking at a landscape as we passed it, tried to memorize the details of a scene. In this case, a lovely rural landscape on the road from Edinburgh to Leith. This little exercise of taking "mind photographs", then putting them onto paper became a favorite pastime of mine on the trip and sharpened my observational skills. Try it. It's a fun exercise, but you've only got two minutes!