As Lyfford Haynes wrote, the notecard was an invaluable resource which could be left in a pocket of “one’s every coat.” Notecards also enabled researchers to churn out large bodies of work: a particularly famous example is that of Niklas Luhmann, who adapted the centuries-old “zettelkasten” technique of recording and tagging individual notes. Over his career Luhmann generated some 90,000 intricately organized index cards and produced over 70 books and 400 scholarly articles.