This is simply an amazing article, about something most of us have never heard about, that will set you mind to work. It's a rabbit hole of unanswered questions, not just concerning a hidden message but why we often labor in secrecy to build anagoges of private meaning. From the point of the view of the artist who created it, this might well be a rumination on the nature of creativity. Certainly, I can speak for the point of view of the composer who derives musical strucure from materials which are embedded in the work, and which form a personal touchstone of meaning known only to myself. Pretentious-sounding, I know, but the truth is that the art I create always has a meaning only known to myself....a 'cryptic ethos'.