Hi!
When you ever had one of those books in your hand, showing the most weird linkage and gears to make a movement you will never need... until you desperately need one and forgot how it worked.
Here is a link to an old book (1871):
Fun to read and sometimes works as a puzzle if you just look at the pictures and try to figure out how they work.
You'll find other books there worth reading.
Enjoy! Nick