When I was younger, a long time ago, I must have been about 16 or 17, I took a train ride in search of an adventure, with love in my heart and some small change in my pocket. I read a few poems, listened to the British and American music from the late 60s and early 70s. Living in the somewhat communist Yugoslavia at the time, the hippies from capitalism sang songs to me, more often through records than in live performances. And so I somehow found myself riding on the Yugoslav Railways train. The internet had not yet reached me. However, there was a toilet on the passenger wagons. And the toilet had a door. And the door had a doorknob. The doorknob had a little sign that said "Occupied" or "Vacant" - depending on whether the toilet was occupied or vacant, in use or not.
Later, after the arrival of the internet, I was writing internet poetry, programmed in its background. (Ergodic – See: Espen J. Aarseth: Cybertext. About the text that happens when someone/the reader does something.) The train door is the first example of this concept I ever saw, before I even realized what it was and before I logged in for the first time.