I made it up
back in '94 '04* when people where doing some spack 3d things and stuff with dual images. Doubt I was the first to do it, but I hadn't seen it before then.
*'94 was off by a factor of ten. Just a decimal error. ;-)
(
Syncubus Yarr! Ye'll be walking Planck's Constant! [GMT-5],
Sun 16 Dec 2007, 5:36,
archived)