“If we are to select our subjects or arrange our groups with a pictorial motive we must absolutely and entirely sacrifice every other consideration, and be prepared to cut out of our composition the prettiest and most interesting item, if by so doing composition pure and simple is improved. And if some subject you are attached to will not admit of composition or will not admit of your treating it pictorially, then photograph it if you wish, but never suppose that it will form a picture.”

Source: Practical Pictorial Photography, 1898, Methods - The practical application of means to end, p. 19

Notes, 1964; as cited on collected quotes on the website of Gerhard Richter: 'on Techniques' https://www.gerhard-richter.com/en/quotes/techniques-5
1960's

Volume II, chapter VI, section 42.
The Stones of Venice (1853)
Context: We are to remember, in the first place, that the arrangement of colours and lines is an art analogous to the composition of music, and entirely independent of the representation of facts. Good colouring does not necessarily convey the image of anything but itself. It consists of certain proportions and arrangements of rays of light, but not in likeness to anything. A few touches of certain greys and purples laid by a master's hand on white paper will be good colouring; as more touches are added beside them, we may find out that they were intended to represent a dove's neck, and we may praise, as the drawing advances, the perfect imitation of the dove's neck. But the good colouring does not consist in that imitation, but in the abstract qualities and relations of the grey and purple.

The Playboy Interview (1992)

Beckmann's lecture 'Drei Briefe an eine Malerin' ('Three letters to a Woman-painter'), New York and Boston, Spring 1948; as cited in Letters of the great artists – from Blake to Pollock, Richard Friedenthal, Thames and Hudson, London, 1963, p. 214
1940s

Aswathy Thirunal Rama Varma, in "Royal musical treat"
About Swathi Thirunal

It is no disparagement to the Americans of English descent to affirm that much of the wealth, leisure, culture, refinement and civilization of the country are due to the arm of the negro and the muscle of the Irishman. Without these, and the wealth created by their sturdy toil, English civilization had still lingered this side of the Alleghanies, and the wolf still be howling on their summits. To no class of our population are we more indebted for valuable qualities of head, heart, and hand, than to the German. Say what we will of their lager, their smoke, and their metaphysics, they have brought to us a fresh, vigorous and child-like nature; a boundless facility in the acquisition of knowledge; a subtle and far-reaching intellect, and a fearless love of truth. Though remarkable for patient and laborious thought, the true German is a joyous child of freedom, fond of manly sports, a lover of music, and a happy man generally. Though he never forgets that he is a German, he never fails to remember that he is an American.
1860s, Our Composite Nationality (1869)

Longing for the Harmonies: Themes and Variations from Modern Physics (1987)

As quoted in: Fred Kleiner (2008) Intl Stdt Edition-Gardner's Art Thru/Ages: Globl Hist. Vol.2, p. 949
1918 - 1935, Realistic Manifesto, 1920