When in Italy [Klee stayed in Italy, in 1901], I learned to understand architectural monuments... Even the dullest will understand that the obvious commensurability of parts, to each other and to the whole, corresponds to the hidden numerical proportions that exist in other artificial and natural organisms. It is clear that these figures are not cold and dead, but full of the breath of life; and the importance of measurements as an aid to study and creation becomes evident.

December 1903. p. 443 - "Artists on Art, from the 14th – 20th centuries"