The author begins the book with a half page disclaimer. Unfortunately, this page is not available in the Amazon preview. The author states, among other things:
"You won't find many exact measurements to follow; you'll have to get things right for yourself using good old empiricism."
and
"...some drawings look as if you could just copy them onto wood and put it all together to work perfectly the first time-- but that might not be the case..."
I made a Limberjill from a pattern in the book. The joints are sloppy, but it does work.
I also made the Mermaid Wigwag. It didn't look quite right, but thinking I might be missing something, I put it together, as shown, anyway. I was right. Other than being a weathervane, it didn't move. The author was correct in stating the arms are at right angles to each other, but the diagrams, all of them, are wrong. Taking it apart, it was easy enough to reassemble correctly. The arms are oriented the same, but are at 90 degress to each other around the axle, rather than 180.
Some of the other "designs" look interesting, but the mechanisms are more complex than I want to try to build on a trial and error basis.