So for all I know this could be a made up quote but
You may not believe this, but Pagey once took me aside and said ‘Look, I’m going to tell you the meaning of this once, and then I shan’t ever mention it again—or at least, not for a long, long time anyway.’ And would you believe that I have since forgotten what it was, and now Pagey won’t tell me- Robert Plant on the Zoso symbol
so as far as I know Robert is the only person who has ever been told.