“The country [ Brittany ] is very beautiful and painterly one see stimulating color tones; but the more abstract one works, the more one transforms the sketch into combinations.”

Source: Flatland: A Romance of Many Dimensions (1884), PART II: OTHER WORLDS, Chapter 19. How, Though the Sphere Showed Me Other Mysteries of Spaceland, I Still Desired More; and What Came of It
Context: My Lord, your own wisdom has taught me to aspire to One even more great, more beautiful, and more closely approximate to Perfection than yourself. As you yourself, superior to all Flatland forms, combine many Circles in One, so doubtless there is One above you who combines many Spheres in One Supreme Existence, surpassing even the Solids of Spaceland. And even as we, who are now in Space, look down on Flatland and see the insides of all things, so of a certainty there is yet above us some higher, purer region, whither thou dost surely purpose to lead me — O Thou Whom I shall always call, everywhere and in all Dimensions, my Priest, Philosopher, and Friend — some yet more spacious Space, some more dimensionable Dimensionality, from the vantage-ground of which we shall look down together upon the revealed insides of Solid things, and where thine own intestines, and those of thy kindred Spheres, will lie exposed to the view of the poor wandering exile from Flatland, to whom so much has already been vouchsafed.

Quoted by Maria Buszek, online - note 19 http://mariabuszek.com/mariabuszek/kcai/Expressionism/Readings/SignacDelaNeo.pdf
The notebook where this sentence appears was only published, in facsimile, in 1913 by J. Guiffrey. Signac therefore must have consulted it at the Conde Museum, in Chantilly. This Moroccan travel document was bought at the Delacroix sale by the painter Dauzats for the Duc of Aumale.
From Delacroix to Neo-Impressionism, 1899

C'est très bien de copier ce qu'on voit, c'est beaucoup mieux de dessiner ce que l'on ne voit plus que dans son mémoire. C'est une transformation pendant laquelle l'ingéniosité collabore avec la mémoire. Vous ne reproduisez que ce qui vous a frappé, c'est-à-dire le nécessaire.
Quoted in Maurice Sérullaz, L'univers de Degas (H. Scrépel, 1979), p. 13
quotes, undated

Source: 1900s, Notes d'un Peintre (Notes of a Painter) (1908), p. 412

Source: In Defense of Marxism (1942), p. 147

Un Art de Vivre (The Art of Living) (1939), The Art of Working

Variant: One cannot collect all the beautiful shells on the beach. One can only collect a few. One moon shell is more impressive than three. There is only one moon in the sky.
Source: Gift from the Sea (1955), p. 114

Source: Gay Science