Wow! I've never seen that one. It'd be fun to try to read that one. One of my imagined hobbies that I never have time for is reading the original works on quantum mechanics, to see how they came up with it.
Thank you for this fascinating answer. I myself could never resist a Dover book, and came very close to buying up their entire math-and-physics catalog. I was also in awe of the historical greats from the outset of my career, and hung on their every word.