It's possible to carve a hole through a unit cube, without splitting it into pieces, so that another unit cube can pass through that hole.  This is know as the Prince Rupert problem and was first analyzed by John Wallis, a contemporary of Isaac Newton.  Here's what the result looks like:

If your computer can play audio, have a look at  Ruperts Cube with music!

Here is the worksheet that produced the cube and the animation: ruperts-cube.mw

In Optical-Illusion--Impossible-Prisms, mcarvalho provides a Maple Learn worksheet to illustrate an intriguing optical illusion.  Here I do that illustration in Maple, and in 3D! 

The graphics below shows 4 bars.  Or is it 3 bars?

Download the worksheet, stare at the graphics for short while to grasp the nature of the optical illusion, and then rotate the 3D graph with the mouse and see the illusion fall apart.

optical-illusion.mw

Some years ago I taught a calculus course for especially talented students. I made up the following problem as an interesting challenge.

Take a circular disk made of paper. Cut out a sector of some angle α from the disk. Roll each of the resulting two pieces into cones. Let V(α) be the sum of the volumes of the two cones. Find the α that maximizes V(α).

Here is an animated statement of the problem, produced in Maple.

Some misguided individuals insist that perpetual motion machines are impossible. Here is a proof that they are wrong!

One of these units hooked up to an electrical generator should be enough to supply all your household electrical needs as well as charge your Tesla in the garage.

If you build one and find out that it doesn't work as demonstrated here, then surely you must have misread the specs. Try it again and again until you succeed.

Download perpetual-motion-machine-corrected.mw

The strandbeest is a walking machine developed by Theo Jansen. Its cleverly designed legs consist of single-degree-of-freedom linkage mechanisms, actuated by the turning of a wind-powered crankshaft.

His working models are generally large - something of the order of the size of a bus. Look for videos on YouTube.  Commercially made small toy models are also available.  This one sells for under $10 and it's fun to assemble and works quite well. Beware that the kit consists of over 100 tiny pieces - so assembling it is not for the impatient type.

Here is a Maple worksheet that produces an animated strandbeest. Link lengths are taken from Theo Jansen's video (go to his site above and click on Explains) where he explains that he calculated the optimal link lengths by applying a genetic algorithm.

Here is a Maple animation of a single leg.  The yellow disk represents the crankshaft.

And here are two legs working in tandem:

Here is the complete beest, running on six legs. The crankshaft turns at a constant angular velocity.

The toy model noted above runs on twelve legs for greater stability.

Download the worksheet: strandbeest.mw