I just listened to an interview with Andrea Wulf about her book on Alexander von Humboldt, “The Invention of Nature”.
She described Humboldt’s notebooks and I thought it sounded so “zettlekasten” and Luhmann-like. He was writing in the 1850s, so maybe there’s something in the “zeitgeist”?

Here’s a quote from the transcript:
“And then you have this extraordinary system of filing, which might sound boring, but bear with me. So his filing system, I think it's basically a computer. It's so clever. So here is, and then amazingly kept it like this. So in the archives in Berlin, you get out these boxes. He called them boxes box eight box, whatever box nine, box nine B.

And in that box, you have open envelopes which have also titles, so say a box is called Slavery. Then you have in that box, an envelope that is called Sugar because of course sugar has to do with slavery. Now in that envelope, but sugar, he will have something about the botany of the plants. He will have something about work conditions, all these kinds of different things. So he would get a letter from someone who worked at a slave plantation in the West Indies with botanical information.

So that goes into the envelope, sugar, botany or something like that. And then he would have someone write him something about the health effect it had on slaves or something. And then he has this kind of box slavery, and then he starts writing his books. And so he can just take out this box and he can use it, but he can file it like a page from a book. He has never problems with tearing our pages from books, put that in a newspaper articular letter, but then he does writing another essay or another book.

And suddenly it is about the botany of I'm making this up now, the botany of the west Indies. So you can just take the envelope out of the slavery box and he can put it into the box botany of the West Indies. So he has this vast archive of information, but he can resort it and refile it, according to the project he's working on which is keywording basically in an analog way, which I think is so clever, which allows him to make these connections, which I think other people can't do because they have a different filing system.”