Who came up with the box and arrow diagrams for electron configurations?
This image is from Atomic Spectra and Atomic Structure by Gerhard Herzberg, ‎John William Tranter Spinks - 1944. It does not really have boxes (just boxes of a table), but spin +1/2 and spin -1/2 are shown as arrows. Of course, I am not claiming this is the first usage, just that in 1944 it existed.