“Now, in order to claim some knowledge of painting, Vitruvius speaks of the consideration of the perfect human body and about how good sculptors and painters in order to make it give it a height of ten faces, and I say that according to them they have read and they say that this proportion is based on knowledge of measurement and that it happens that without it it is not possible to have proportion or consideration because those who are not cognizant of this do not count.”
quoted by Liane Lefaivre and Alexander Tzonis, in The Emergence of Modern Architecture: A Documentary History from 1000 to 1810 https://books.google.com/books?id=4xB9k7-Neb8C&pg=PT184; Routledge, New York, 2004) p. 165
Help us to complete the source, original and additional information
El Greco 9
Greek painter, sculptor and architect 1541–1614Related quotes

15 April 1851, as quoted in Artists on Art – from the 14th – 20th centuries, ed. by Robert Goldwater and Marco Treves; Pantheon Books, 1972, London, pp. 230 – 231
1831 - 1863, Delacroix' 'Journal' (1847 – 1863)

official document, 1567; as quoted by Bruce Kohl in Titian and Venetian Painting, 1450-1590; publishers Westview Press, 1999, p. 117
In 1567 Titian applied to the Venetian senate for a fifteen-year copyright privilege for engravings, made after his work. The Dutch artist Cornelis Cort produced prints after Titian's work, all made in collaboration, in 1555-56 and 1571-72
1541-1576

this harmonic proportion may be expressed as <math>\frac{12}{6}=\frac{12-8}{8-6}</math> or inversely.
Nicomachus of Gerasa: Introduction to Arithmetic (1926)

Commentarius in Posteriorum Analyticorum Libros (c. 1217-1220)

Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book I, Chapter II, Sec. 2