1. Create a one-time-pad, or key. This is a set of randomly chosen 1's and 0's. Now, make a bitmap out of this data set, with 1 denoting a white pixel and 0 denoting a black pixel. It will look like static.
2. Distribute a copy of the key to the person you are trying to communicate with via a secure channel. (This is the hard part, security wise).
3. create your message as a black and white (not greyscale) image. It should have the same dimensions as your key.
4. Pixel-wise XOR the key with the message. If the key was well randomized, the resulting cypher will also appear to be perfectly random static.
5. Send the cypher to the person who is holding the copy of the key.
6. When that person receives the cypher, if he XOR's the cypher with the key, out will pop the original message!
The only visual difference to this method vs that in the linked article is that the message won't start to show up when you're a pixel or two out of alignment because there is no four-pixel subdivision. You have to line things up spot-on.
The Vernam cipher was originally published in 1926, so it's defintely older than "Visual Cryptography". However, I don't know if the visual demonstrations of it (I've only seen them in lectures, not surprisingly, with transparent overheads!), predate visual cryptography. I've seen a couple of lecturers use this technique to demonstrate how a one-time-pad works and, crucially, why you can't reuse keys more than once.
Does anyone know if this Visual Cryptography offers anything useful that a one time pad doesn't? The linked page is very cool and all, and I wish one as well constructed existed for one-time-pads! (Possibly one does, but I was too lazy to spend more than a minute searching for it.)