Edsger Dijkstra wrote over 1,300 numbered manuscripts (the EWDs) all by hand, with a fountain pen. He would write a piece, photocopy it, and mail copies to a small circle of colleagues.
He believed the act of handwriting forced clarity.
The EWDs I enjoyed reading a few years ago. The ones that talk about his takes on the not so technical stuff, why we should call it computing science instead of computer science, for one.