This work is registered in the Archivio Alighiero Boetti, Rome, under no. 5941.
"Twenty-five is the square of the holy number five and is therefore also the centre of the magical squares. It consists of the sum of the numbers 1+3+5+7+9 and therefore contains all the holy numbers which can be used in magic"
(Boetti quoted in A. Boetti, Alighiero Boetti: Mettere al Mondo il Mondo, Frankfurt 1998, p. 117)