Chris, I read it some 40 years ago when as a school boy I began with my Zettelkasten journey. It is about the technique as well as the intellectuell framework behind it and was surely pointed to business aspects as well as running the civil service but also outspoken to the worker of the mind, the scientist and philosopher. Filing and indexing is crucial to all of these varied aspects of cultural life. But don't expect hitherto unknown magical practices to be revealed. It was commune practice then and you could find handbooks on indexing and filing in organisations also in America and England at that time. The new found way of personal knowlegde management just doesn't know about its predecessors with pen, ink, typewriter and other unbeliefable tricks.

Über die Karteikartentechnik wurde sogar ein wunderbares Buch geschrieben: Karteikunde, Das Handbuch der Karteikartentechnik von Dr. Walter Porstmann.

The first time the ratio of length to width was written in a letter dated 25 October 1786. This letter was from the German Georg Christoph Lichtenberg to Johann Beckmann. He wrote here about the advantages of basing paper on a √2 ratio. Lichtenberg is known for the ratio between length and width of a surface which remains the same after the narrated halving of the surface. The result is 1:√2.