HELP please booky people: historical puzzle books ...

[Bink]

... where there is a Deliberate Mistake or several, like I don't know horses being ridden in Aztec-land

I know I have seen these, and they are probably something totally obvious like Usborne, but I can't seem to track them down

stress ...

I found it, just in case anyone else is interested - called Errata - A Book of Historical Errors, illustrated by someone called Hemesh Alles. There is also a follow-up one, which is out of print.

Well there's a stage direction in Julius Caesar that has a clock striking midnight.

Also there are movies set in ancient times that have lots of Americans in them. I'm sure you've noticed.