The Zettelkasten: Joan Rivers' Million Index Cards and the First Wiki

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The Zettelkasten, German for slip box, is a system of modular, cross-referenced notes that the episode traces from the Renaissance to the internet. Bound commonplace books trapped ideas in chronological order, so in the 1500s Swiss scholar Konrad Gessner cut his notes apart with scissors and glued the slips onto new sheets by topic. In the 1640s English inventor Thomas Harrison built the Ark of Studies, a cabinet where slips hung on metal hooks under subject headings, later refined by Vincent Placcius in 1689 and used by Gottfried Wilhelm Leibniz. In 1767 Carl Linnaeus standardized slips at five by three inches, and the Linnean Society of London still holds more than a thousand of his cards. A 1921 guide by Antonin Sertillanges described hierarchical numbering, tagging and cross-referencing.

Branching numbers such as 1, 1a and 1a1 let a new thought sit right behind the note it relates to, linking distant subjects. German sociologist Niklas Luhmann built a box of about 90,000 cards from the early 1950s and called it a communication partner while publishing around 50 books and 550 articles. Comedians ran on the same engine: Phyllis Diller filed 52,000 cards, Bob Hope kept more than 85,000 pages of jokes, and Joan Rivers amassed over a million 3x5 cards. In the 1980s Xerox PARC built NoteCards with clickable links between digital cards, and in 1994 Ward Cunningham, inspired by a HyperCard stack, invented the wiki.

• Roland Barthes kept about 12,000 slips from 1943 until his death and drew on 330 of them for his posthumous Mourning Diary.
• Hans Blumenberg kept 30,000 cards, and Walter Benjamin and Arno Schmidt also relied on slip systems.
• Comedians jotted jokes on receipts and matchbooks, then filed them on cards by topic such as air travel.
• Ronald Reagan kept a large card collection of quotes and aphorisms for his speeches.
• Cunningham described the wiki as the simplest online database that could possibly work.