I'm pretty sure it was described fairly comprehensively in Art and Artifice, though I could be wrong. I was recently reading something that certainly had it described, and I'm pretty sure that was it - but it could just as possibly be Greater Magic, Art of Magic or Modern Magic - as I've been skimming them while re-reading A&A.
Originally Posted by Magic Katie
Sorry if I've made things more confusing. As Katie's said - Google is a fantastic tool for trcking things down.
All the best,
I have no use for people who have learned the limits of the possible.