Plan 9/Inferno chiefly, but more broadly if you read RFCs and other design documents written around that era it's pretty clear that engineers envisioned a decentralised, interoperable, resilient, "modular" computing environment. Some concepts read like fables/alternate universes as they are quite removed to what we have hands-on experience with, but seeing a distributed filesystem in action is a trip. If you have an interest in this stuff, either from an historical or technical standpoint, I highly suggest spending a weekend messing around with a bunch of p9 VMs :)