“Of all the various ways which the imagination has distorted truth, there is none which has worked so much harm as an exaggerated respect for past ages. This reverence for antiquity is repugnant to every maxim of reason, and is merely the indulgence of a poetic sentiment in favour of the remote and unknown.”

Source: The Social Contract

quote from his exhibition-text of 1836; as quoted in: Ronald Parkinson: John Constable: The Man and His Art, V&A, London, 1998 (ISBN: 1-85177-243-X), p. 89 (taken from Wikipedia)
When Constable exhibited his watercolor 'Stonehenge' (he painted in 1835) one year later, he appended this short text to the title of his famous watercolor
1830s

Said to Sir Louis Mallet by Cobden on his death bed within two days before his death, quoted in Richard Gowing, Richard Cobden (London: Cassell, 1890), p. 130.
1860s

An Address on Abraham Lincoln before the Republican Club of New York City (12 February 1909) http://web.archive.org/20050322051431/www.historycooperative.org/btw/Vol.10/html/35.html
Context: Of all forms of slavery there is none that is so harmful and degrading as that form of slavery which tempts one human being to hate another by reason of his race or color. One man cannot hold another man down in the ditch without remaining down in the ditch with him.

Hat matt nicht die Augen, um sich sie auszureißen und das Herz zum gleichen Zweck? Dabei ist es ja nicht so schlimm, das ist Übertreibung und Lüge, alles ist Übertreibung, nur die Sehnsucht ist wahr, die kann man nicht übertreiben. Aber selbst die Wahrheit der Sehnsucht ist nicht so sehr ihre Wahrheit, als vielmehr der Ausdruck der Lüge alles übrigen sonst. Es klingt verdreht, aber es ist so.
Auch ist es vielleicht nicht eigentlich Liebe wenn ich sage, daß Du mir das Liebste bist; Liebe ist, daß Du mir das Messer bist, mit dem ich in mir wühle.
Letter to Milena Jesenská (14 September 1920) http://www.abyssal.de/zitate/liebe.htm
Variant translations:
In this love you are like a knife, with which I explore myself.
Letters to Milena (1952)

Light (1919), Ch. XXIII - Face To Face

The Notebooks of Leonardo da Vinci (1883), XX Humorous Writings

Source: Vegetarianism, p. 39

Context: Years later, when "Dilbert" was in thousands of newspapers, people often asked me if I ever imagined being so lucky. I usually said no, because that's the answer people expected. The truth is that I imagined every bit of good fortune that has come my way. But in my imagination I also invented a belt that would allow me to fly and had special permission from Congress to urinate like a bird wherever I wanted. I wake up every morning disappointed that I have to wear pants and walk. Imagination has a way of breeding disappointment.