Some students of an High School asked me some books from famous mathematicians that they can read (so advanced high school level focused mainly on real-analysis). They were asking things like Cauchy, Fermat... but I think the language would be technical in an akward ancient way for them so that probably will not be suitable. I thought that maybe Riemann dissertation could do but maybe it's too advanced. I then thought Galois, but again the original papers are quite difficult to understand if you don't already have the right picture in your mind.

I'm not sure there's effectively a book from an historically famous mathematician that could fit the request. They didn't specifically requested that the argument should be mathematical even if I think they implied this, otherwise I could suggest something of Poincaré which rather philosophical but at least readable. 

They didin't specify the period (even if I think they might want to already know the name of the writer). In modern period maybe I would suggest Mumford the Indra's Pearls. But I'm quite sure they don't know Mumford...

I'm now thinking that maybe some kind of physicist would be better. But they were asking mathematicians.

I really don't have a clue of what to suggest. Please help me!

**Edit.** Someone correctly asked me why I'm "*limiting to Mathematicians they've heard of*". I totally agree with who's asking. Old mathematics would be kind of akward I think. The problem is not that "*I'm limiting*", the problem is that "*this is what they asked*". It's something like "*We have seen their theorems, heard a lot about them, we would like to read something written by them*". As pointed out is that probably this request cannot be fulfilled entirely or is not a good idea to fulfill their request. So any suggestion will be take into account. If it was physics Schroedinger "What is Life" and some Heisenberg essays would be in order... in mathematics I've no clue if exists something similar... I think maybe Poincaré is the only one...