A book written in 1910 could teach you calculus better than books of today

I find it useful, when I learn about something , to go to the origin of the thing I'm learning. For example, I want to learn about x86 assembly language and processor. Then I read first ever manual on x86. and manuals from processors that preceded it.

This is true of a lot of subjects. The old books and videos are better.

yeah except now try change of variables. that's where ppl get in trouble