The Blackwood convention (which uses a bid of 4NT to ask for number of aces) is probably the most utilized and most famous convention in the history of bridge. When Easley Blackwood devised it, he submitted a write-up about it to the Bridge World magazine. They rejected it!
We're getting ready for our move to the new building. As I was packing things in my office, I came across the rejection letter dated May 24, 1935. The ACBL archivist has the original. This is a scan of a photocopy (click to enlarge):