Things I'm looking for
During third grade at Shady Hill School, in Cambridge, MA, I was in a class that got a special accelerated math class. Our "textbook" was a paperback, 8.5 x 11 book, with (as I recall) rather nice illustrations done in blue and green. I recall that on the last few pages, the book discussed how far you could see (i.e., distance to the horizon) from a spaceship 50,000 feet above the earth (using similar triangles and the pythagorean theorem). I have the odd feeling that the book was produced by 3M Corporation, although as I reflect on this, it seems very unlikely.
There was a pair of photos at the Museum of Modern Art in New York the last time I was there -- about 15 years ago (sigh). The first showed a classroom in which someone had been teaching an art class. The teacher, using a blackboard and white chalk, had been showing how to shade various things, like a sphere, a cube, a cylinder. But s/he had used the chalk as if it were a pencil, so that the students, taking notes in pencil, could emulate it. The drawings on the board therefore looked very odd. The second picture was a "negative print" of the first; everything in the room looked completely odd, but the drawing on the blackboard now appeared as black-on-white, and made perfect 3D sense. I'd like to know the photographer and the name of the work.