The original zettelkasten system comes from the German sociologist Niklas Luhmann, who credited his productivity and success to this system and called it his “writing partner”.

His “Zettelkasten” system consisted of about 60,000 slips of paper (kept in a number of wooden boxes) on which he wrote short notes (Zettelkasten notes are atomic).

Each note had an ID, and he would relate notes and concepts together by referring to these IDs (Zettelkasten promotes reuse).