Imagined by Vannevar Bush in "As We May Think," in 1945, the memex is a desk-sized scholar workstation containing a microfilm library. Text and images are displayed on two screens, and can be annotated by hand. Most importantly, texts and images can be linked, so that bringing up a text on one screen brings up a linked text on the other. These links can be organized into trails, and the trails shared with others.
A 2014 to recreate the Memex from description. source
Bush's design for the Steelcase memex suggests that online teachers and learners work at reciprocal workspaces. It's not a matter of the teacher has the big desk and student at the small one; they both use their own memex as a Personal Learning Environment. Part of learning, then, is creating and learning to use this personal workspace with the guidance of an instructor - as a glassblower creates her studio and a botanist her lab.
The reciprocity of teaching and learning spaces is significant here. Compare this design to traditional classrooms where only the Teacher has the Big Desk, a design that is re-created in online learning using a Content Management System.