In Virginia Woolf’s Mrs Dalloway (1925), a plane flies over post-World War One London and seems to write letters in the sky: Dropping dead down the aeroplane soared straight up, curved in a loop, raced, sank, rose, and whatever it did, wherever it went, out fluttered behind it a thick ruffled bar of white smoke which curled and wreathed upon the sky in letters. But what letters? A C was it? an E, then an L? Only for a moment did they lie still; then they moved and melted and were rubbed out up in the sky, and the aeroplane shot further away and again, in a fresh space of sky, began writing a K, an E, a Y perhaps?
I think Mrs Dalloway's experience is called "pareidolia" -- seeing meaningful shapes in natural or human-made phenomena. Steven Heller & Gail Anderson have collected examples of that plus letterforms composed of unusual material in "Typographic Universe". It's hard to say which is a subset of which -- Graphosphere or Typographic Universe. (http://books-on-books.com/2021/05/08/books-on-books-collection-steven-heller-gail-anderson/)
"Graphosphere" is a useful concept, thanks. In the main, I find the contemporary graphosphere ugly, and typographically illiterate. The urge to scrawl graffiti over everything doesn't help. I have a particular liking for sites where remnants of an older graphosphere are exposed, for example the original tiled walls and adverts revealed by renovation on London underground stations, or wonderful made-to-last shop signs still lying dormant beneath modern illuminated facades. Ironically, much of this older "text" may predate mass literacy. Perhaps it was made beautiful both to acknowledge and alleviate its intrusiveness, but also to celebrate the ability to read?