Reddit mentions of The Principia : Mathematical Principles of Natural Philosophy

There are a number of useful guides available but they're all written by aficionados, or other successful players, though - not the designers.

This is the best guide for a high Int/Cha talkie game, I think.

This is well recommended for a more aggressive style of game, but a lot of people mistakenly misapply it to trade - it's really just for combat.

This is great for a sneakier game.

This is a badly written hack job that too many players put a lot of stock in; supposedly it was written by the designers, but it was actually written (and re-written) by a lot of different guys and is very contradictory - i'd avoid

Finally, this won't help you play, but it really explains the deeper mechanics.

And this goes into detail on the meta-game.

Hope that helps!

I'm a big fan of reading historical physics papers. I have this extremely well-annotated version of Newton's Principia, this collection of Schrödinger's original QM papers, and this fairly easy to find collection of relativity papers (mostly Einstein). Oh yeah, and these Dirac lectures.

Besides that, I just use my university subscription to find old papers, which is usually successful if they were published in English or sufficiently famous. I would say that I have a lot of "classic" papers saved just through finding them on Google Scholar or whatever. I could try to go through and list them, but I'd say it's mostly "usual suspects" plus important papers from my own interests (condensed matter/stat mech/QFT).

I recommend:

http://www.library.usyd.edu.au/libraries/rare/modernity/newton3.html

Or more usefully:

http://www.amazon.com/Principia-Mathematical-Principles-Natural-Philosophy/dp/0520088174

or any basic physics textbook.

This might fit into three of your categories: Issac Newton's masterpiece, The Principia. It's really astounding that this book is even accessible. Sorry if it's not as wishlist-friendly as you were hoping for, but I thought you might be interested since you had 'math' as one of the categories.

edit: $10 range item; $5 range item I really really want it!

Science was originally another subset of philosophy called "Natural Philosophy" at the time. It has since grown in to an independent discipline of course, but I never let those people forget where they came from!