Kant was so famous for taking a daily walk at precisely 3:30 p.m. that the residents of Königsberg could set their clocks by it.

Hence the popular expression "It's good to be punctual, but you don't have to be a Kant about it"

Lots of famous historical figures walked. Darwin, Jefferson, Nietzsche, Dickens, Thoreau. More recently (obviously): Jobs.

I wrote a small piece a several years ago on it but have found walking immensely helpful in my debugging efforts. And there's so much research that backs it up.

Darwin was said to have a circular path in his garden that resembled a trench it was so well-worn.