Or maybe it should be text and meta-text. Anyhow, John D. Muccigrosso wrote to point out something that's obvious in retrospect, namely that all those pages that say "This page intentionally left blank" are thereby not, in fact, left blank.
In looking for examples, I discovered that the earliest example of this that Google Books can find seems to have been published around 1922.
- an artefact of the scanning, indexing, or searching methods used?
- the result of a change in wording, with the same idea expressed with different words in earlier times?
- a genuine cultural innovation, so that before 1922, intentionally-blank pages were simply left blank without any self-identifying advice to the reader?
At some point, Federal regulations seem to have imposed such a requirement — presumably on certain classes of government documents, though I can't tell exactly from the "snippet view" at the link just provided.