Double Quotes
In accordance with the foregoing investigations on mathematical principles, let bronze vessels be made, proportionate to the size of the theatre, and let them be so fashioned that, when touched, they may produce with one another the notes of the fourth, the fifth, and so on up the double octave.
Vitruvius
To sum up: numbers appear to represent both an attribute of matter and the unconscious foundation of our mental process. For this reason, number forms, according to Jung, that particular element that unites the realms of matter and psyche. It is "real” in a double sense, as an archetypal image and as a qualitative manifestation in the realm of outer-world experience.
Marie-Louise von Franz