Although not exactly a useless fact to everyone, you can buy a kit to make yourself an authentic, historically accurate trebuchet, even if you are not inclined to do the necessary engineering or research medieval weaponry yourself.
That's a lot of money, for something so small.
I think it's a bargain, considering that the kit consists of over one hundred forty, precision computer cut pieces, complete assembly instructions, including pictures. Models with this degree of authenticity are usually pricey, ya know.
If you would prefer to do all the cutting on your own shop equipment and scale it as you see fit, you can also purchase sets of plans by download or CD for only around twenty bucks.
... or for about forty bucks you can buy their complete course, with many plans, lots of theory, virtual simulator programs, etc. Even some tips on competition.
Useless!