Sutherland constructed the first VR system. In 1968, he finished the first head-mounted display in 1968. Because of its weight, it had to be suspended from the ceiling and was appropriately nicknamed “Sword of Damocles”. This display already included head tracking and used see-through optics.
https://en.wikipedia.org/wiki/The_Sword_of_Damocles_(virtual_reality)
https://en.wikipedia.org/wiki/Ivan_Sutherland
https://www.youtube.com/watch?v=AFqXGxKsM3w
Ivan Sutherland developed in his 1963 thesis at MIT’s Lincoln Labs, “Sketchpad, A Man-Machine Graphical Communication System”