Computer-aided out-of-body experience
A little more than a hundred years ago, an American psychologist George Stratton pondered the question: how stiff are the algorithms of human vision in the brain? As a result of his curiosity, he built an optical device with mirrors that turns the image upside down and put it onto his head. On the seventh day of continuous wear Stratton got adapted to a new perception of the world, and the picture began to seem completely natural. When he removed the device, for a while the world seemed strange to him, however, later his perception got back to normal.
I've done the similar experiment but even more crazy. For 4 days I was wearing the out-of-body virtual reality glasses all the time (the article about the experiment in Russian). The picture that I was seeing for the whole time looked like this