I read about something a long time ago, maybe in a lucid dreaming context, but it was about a man who was sitting on a train in the early 20th century daydreami

I read about something a long time ago, maybe in a lucid dreaming context, but it was about a man who was sitting on a train in the early 20th century daydreaming, and the shadows from trees rapidly passing over his eyes basically kickstarted his ability to visualize with his mind's eye. I think he might have even gone on create a device with a spinning circle with slits on it and a lamp behind it in order to play with the effect. Anyways, I tried it a long time ago, and it definitely enhanced my ability to truly "see" mental imagery. Give it a shot! All you need to do is close your eyes and relax in front of something that is generating a lot of bright/dark areas in motion. Even sitting in front of a TV in a dark room with the TV muted would probably work.