As a note, I just today received the 6th edition of "The Bicycling Guide To Complete Bicycle Maintenance and Repair" by Todd Downs. On page 72 is a photo showing how to release a cantilever brake, exactly as shown above. The 5th Edition of this same book doesn't have this photo, it states textually what to do. The Zinn book doesn't have either diagrams or photos of how to release cantilever brakes. It does have diagrams of cantilevers, but they don't show how to release these.
So if I had just had the 6th edition of Downs', I wouldn't have fussed so much! The 6th edition is a big improvement over the 5th but you all probably know that. Even more -- the 6th edition is 5 years old now and begs for an update. Rodale Press spams me with email ads for this book at least least twice a week, ad nauseum. So maybe they are trying extra hard to get rid of old print copies and make way for a 7th edition???? I don't know. I do know they spam me. And spam me.
Bob