There was a thing called a delay line memory that IBM used in the System Three. It was a piece of piano wire about 30 feet long I believe (coiled up of course)that was twisted on one end with a little solenoid for about a msec or so. It would take a bit of time for that twist to wave its way down to the end of the wire where that twist would be detected. If I remember correctly you could store about a Kbyte or so. I may be off on the numbers though. I'll see if there is anything on google.
