I was reading about the Emacs org-roam mode, and came across the Zettelkasten method of notetaking. I hadn’t seen this term before, but the idea of taking notes with cross-referenced index cards sounded familiar. Where did I read about it? Ah yes… in Umberto Eco’s Foucault’s Pendulum, the main character Casaubon (an ex-academic who makes a living as a “detective of knowledge”) uses boxes of index cards to keep track of ideas. I wouldn’t be surprised that Eco himself did this religiously. He apparently recommended it to PhD students.