My favorite trip toy hung right in my bedroom window: a coat hanger, below which I'd hung three of those silvery spherical Christmas ornaments, each suspended by fishing line at a slightly different height.
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Below the ornaments, sitting on a small table, was a very large, thick magnifying glass. It was about eight inches in diameter, and had no handle-- it was just this orb of heavy, clear glass.
As you can well imagine, the toy, while amusing, could also be a tripper's trap. I'd lure trippers into my room, hand them the magnifying glass, and tell them to look into the closest sphere.
One of the properties of a spherical mirror is that it reflects its entire surroundings, so people saw themselves looking through the magnifying glass at the sphere, they saw the rest of the room in the sphere, and they saw through the window in the sphere. But they also saw the reflection of the sphere they were looking at, with all the aforementioned images, in the reflection on the next sphere, which was in turn reflected on the next sphere, and so on-- ad infinitum. People stared into the thing for a really, really long time, getting lost in the nested reflections of the spheres.
I recommend trying this, even while not hallucinating. It can be amusing for a few moments. Just make sure you have a powerful magnifying glass.