Watch a Straight Rod Pass Through a Curved Hole [VIDEO]

This may be the simplest video I've ever seen and yet I'm completely dumbfounded by it.

According to the description on YouTube, this contraption is set up at a museum in Spain and is one of the museum's few redeeming qualities.

It seems like this should be impossible...A straight rod passing through a curved hole. Yet, this machine manages to do it seamlessly.

I, honestly, cannot stop watching this. I need to make something like this for my desk, except I'd probably never get any work done. Well, less than I do now.

[YouTube]