The Mother of All Demos - Incredible demonstration of a computer from 1968
"…A conference by Doug Engelbert [SRI] in December 1968 shows a live demonstration of the "oN-Line System" (NLS), which shows so many features that are comparable to modern day computing. The demonstration included a live video call to collaboratively work on a document, a mouse interface to select text and "hyperlink" to other pages, all in a GUI that would be familiar to modern computer users."
https://youtu.be/B6rKUf9DWRI