Did some testing on perpetual motion. Here's the simplest and most compact perpetual motion plant I could find, in words:
1. Dig a single-tile hole in the ground (with the Channel designation).
2. Fill the hole with water via dwarven bucket brigade (the Pond activity zone). They'll only fill it to 6/7, but that's okay.
3. Build a gear assembly next to the hole for support, and build a waterwheel with its center tile over the hole. The waterwheel will extract energy from the water (don't ask how).
4. Use the power for your nefarious plans!
5. ? ? ?
6. Profit!
Tested and works IF outside. Tested with Shinz's test map and one of my older forts on 40d16. Get nothing if inside, works great outside.
Also tested in an outdoor hole that I channeled instead of constructed. Did not run.
So it appears that an outdoor 3x3 "cell" with a constructed floor and walls and then filled with water to 6/7 will run a waterwheel...
Worth a bug report? or think it matters for the next version?
I figured out another requirement...
Not just outside, you have to have a brook or stream as well, so outside with already flowing water.
I replicated shins structure from the movie on my 3x3 flat no-brook map and got nothing, so i tried a multi level map (again no brook) and again got nothing. So i looked around on shinzis map some more and noticed the river, so genned a new world and embarked on a stream and was able to replicate this. But yes it does have to be outside.