It was never spelled out in the minutes or anything like that, but
went something like:
From the minutes of November 91 meeting in Santa Fe:
(d) Character set issues
The Working Group specified the definition of a character set
for the purposes of quad-x to be a unique mapping of a byte
stream to glyphs, a mapping which does not require external
profiling information.
Note: quad-X was the name of MIME before Nathaniel had a brainstorm.
The minutes of all working group meetings are available from the shadow
repository near you. Try nnsc.nsf.net:~/ietf/822ext*
Greg V.