True, although "the largest QR code" is substantially more dense than most people have ever encountered: https://en.m.wikipedia.org/wiki/File:Qr-code-ver-40.svg . People might not realize that QR codes scale up and down very gracefully; most QR codes that people have ever seen probably encode less than 80 bits.
Reminds me of a project a friend and I took part in, sending each other source code via postal mail. I ended up sending a QR code printed on film negative [0] to pack about 1k of bytes. Bellard's code is way more "information-dense" of course..! :-)
That's an incredibly kind comparison. Thank you! Do you have a reference where Feynman talks about this? I'm finding this [0]:
"Arline entered the nearby Albuquerque sanatorium, from where she wrote him letters in code — for the sheer fun of it, because she knew how he cherished puzzles, but the correspondence alarmed the military censors at the laboratory’s Intelligence Office. Tasked with abating any breaches to the secrecy of the operation, they cautioned Feynman that coded messages were against the rules and demanded that his wife include a key in each letter to help them decipher it. This only amplified Arline’s sense of fun — she began cutting holes into her letters, covering passages with ink, and even mail-ordered a jigsaw puzzle kit with which to cut up the pages and completely confound the agents."
In Montreal, the really really great people at Borealis [0] made it extremely easy. I sent them a 300 DPI file by email, and they printed negatives from those files in a few days. Each negative cost about $8 to print.
Finding a lab that did this online was pretty difficult at the time. If others have recommendations -- please chime in! Otherwise, I would strongly recommend considering Borealis (who I'm sure can ship the negatives by mail -- otherwise reach out and I can facilitate the mailing as I live here ha)
It was an art project -- called "Postal Codes" -- where an artist friend and I would correspond by creating sketches (typically using p5.js or three.js) and sending them by "snail" mail. There is a bit more information here [0], here [1] and here [2].
