I did one, a very long time ago, in Bryce. Pick the Looking Glass image from http://www.main.artbeeweb.nl/?p=3990 

Each one was made of two slices of a ball, glued together. Ball was made of simple glass, index 1.5 or so.

Each looking glass has a focal length. If you're inside that range, the image turns upside down. So if you set each magnifying glass withing the focal range of the next one, you'll get a series of flipping images. In the first, you can see the second upside down which shows the third one straight up. The renderer must do that automatically.

But do note that you have to crank up the max amount of ray bounces in the render settings, otherwise the inner ones will turn black. Each glass adds four bounces (ingoing, two halfay and outgoing) so this image required at least 20.

have fun.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though