Found out about a project called ZOG that was an early pre-internet hypertext system. Information is placed on "frames" that are linked together into a large local network. What's interesting about these old systems it that they're really minimal, far more so than any kind of information organization system today. They had to be designed without any of the complex control systems that modern computers have, yet still be usable by the non-expert in a time before the familiarity of the now ubiquitous PC desktop interface. In this case, ZOG was put into use on an aircraft carrier and used as a kind of local network where people could lookup information and leave "mail" for others. Many of the design choices made by the creators of this system can directly inform how Pith's document system works in terms of balancing simplicity and richness.
Reading these old papers is also fantastic, there's some really beautiful artifacts out there.