Different one. Across my bedroom is the cable box, which has an LED display. So in a pitch dark room I close my eyes until I can see only the LED and nothing else. Then I just focus on it.
First thing that happens is I see two of them. Fair enough, that's just my eyes unfocusing.
Then they both keep trying to drop, quickly but smoothly, to the bottom of my field of vision. I'm intrigued by this. After all, the light is a constant. Therefore I must be witnessing my eyes rolling back in my head. Fascinating. Each time I become aware of it, the lights come back up to the center where they belong - but only deliberately, when I will them to. I can let them stay down there if they want.
Then, they begin to move independently. This is a little weird. They get farther apart, then closer together, like two little spaceships floating around my field of vision. I wonder if my eyes are supposed to be doing that, and since I'm not sure if it's bad for my vision, I give up on this little exercise.
I have to try that again. It was definitely unexpected and very close to the state I was aiming for, since I would periodically become aware that I was no longer looking at an otherwise blank room, but rather that my awareness had come to be focused entirely on the lights, and the surrounding area was not just dark, but nothing at all.