Screenshot: https://osde8info.files.wordpress.com/2007/02/6a00d4141b9517...
There's a writeup on how it works:
http://www2.epcc.ed.ac.uk/~spb/xmountains/about_xmountains.h...
I don't know how old it is, but the timestamp at the bottom of the HTML file above is 1997.
