[tangentspace]

No, I was never under that impression. I once had a discussion about the creation of the book with one of Federer's students who had also helped proofread it. The book was essentially an outgrowth of his personal and course notes, since of course he couldn't keep all this in his head.

What he likely did have in his head was an index into the contents, that's the crux of my observation. If I am very good at organizing my workshop, I can quickly grab the tools and materials needed for a particular task without breaking my flow of thought. Same basic principle applies to mathematicians and other intellectual workers, just as it does with physical trades.