(Continued)

The diamond from the Chi-rho page
of the Book of Kells —

The diamond at the center of Euclid's
Proposition I, according to James Joyce
(i.e., the Diamond in the Mandorla) —

Geometry lesson: the vesica piscis in Finnegans Wake

The Diamond in the Football —

Football-mandorla

“He pointed at the football
  on his desk. ‘There it is.’”
         – Glory Road