|The German great genius Friedrich Nietzsche who, in 1889, after famously declaring, in 1882, that “God is dead”, epitomizing the emerging view that the Christian God was no longer a viable source of any absolute moral principles, supposedly, went insane (Ѻ) (Ѻ), dying (dereacting) the year after. (Ѻ)|
German philosopher Friedrich Nietzsche is said to have gone insane in 1889. The following are a few relevant quotes:
“And those who were seen dancing were thought to be insane by those who could not hear the music.”— Friedrich Nietzsche (c.1885)
“In individuals, insanity is rare; but in groups, parties, nations and epochs, it is the rule.”— Friedrich Nietzsche (c.1885)
“A casual stroll through the lunatic asylum shows that faith does not prove anything.”— Friedrich Nietzsche (c.1885)
In 1840, German physician and physicist Robert Mayer, one of the first to state the first law of thermodynamics, while working as a ship’s doctor on a Dutch vessel which visited the East Indies, had conceived of the mechanical equivalent of heat, equation shown, by study of the color of the blood of his crewmates and the temperature difference between the tropics and Europe. In 1842, after returning to Germany, he began to publish his scientific theories on in obscure journals, such as Annals of Chemistry and Pharmacy, but his theories went largely unnoticed as these journals were not read by physicists. Those who did notice, however, ridiculed his work, as it was not based on experimental data. 
|In 1850, German physician-physicist Robert Mayer, after discovering that James Joule had claimed discovery of the mechanical equivalent of heat, while his work was still unknown, jumped out of a third-story window, and was later put in an insane asylum.|
During this period, one of his sons and two of his daughters fell ill and died before the age of three. He also discovered that English physicist James Joule had claimed discovery of the mechanical equivalent of heat, while his theory was still unknown. In 1850, during an attack of insomnia, Mayer jumped out of a third-story window and fell almost thirty feet to the ground and broke both his legs. It is said that in 1851, he was placed in an asylum, but later released.  He survived, but soon was forced to begin spending long series of voluntary and involuntary hospitalizations and even occasional restraint by strait-jacket.  Curiously, in Poggendorf’s authoritative 1863 Dictionary of the History of Science it was incorrectly claimed that Mayer had already died—in an insane asylum.
In 1961, American philosopher Robert Pirsig, a former child prodigy cited with an IQ of 170 at age 9, suffered a nervous breakdown and spent time in and out of psychiatric hospitals over the next three years. He was diagnosed with paranoid schizophrenia and clinical depression as a result of an evaluation conducted by psychoanalysts, and was treated with electroconvulsive therapy on numerous occasions, a treatment he discusses in his novel, Zen and the Art of Motorcycle Maintenance. In his Lila: an Inquiry into Morals, he employs the term “insanity” one some 13+ pages.  The following are a few representative quotes:
“I think present-day reason is an analogue of the flat earth of the medieval period. If you go too far beyond it you're presumed to fall off, into insanity. And people are very much afraid of that. I think this fear of insanity is comparable to the fear people once had of falling off the edge of the world. Or the fear of heretics. There's a very close analogue there.”— Robert Pirsig (1974), Zen and the Art of Motorcycle Maintenance (§14) (Ѻ)
“Sanity is not truth. Sanity is conformity to what is socially expected. Truth is sometimes in conformity, sometimes not.”— Robert Pirsig (1991), Lila: an Inquiry Into Morals (Ѻ)
“When one person suffers from a delusion it is called insanity. When many people suffer from a delusion it is called religion.”— Robert Pirsig (1991), Lila: Inquiry into Morals; cited in The God Delusion (pg. 28) by Richard Dawkins
The following are related quotes:
“There was never a genius without a tincture of madness.”— Aristotle (c.310BC)
“There is no great genius without a touch of madness.”— Seneca the Younger (c.50AD) (Ѻ), likely Aristotle paraphrase
“We do not have to visit a madhouse to find disordered minds; our planet is the mental institution of the universe.”— Johann Goethe (c.1800)
“Emptiest word rubbish and silliest gallimathias that have ever been heard outside the insane asylum.”— Arthur Schopenhauer (1839), commentary on the writings of Georg Hegel 
“I became insane, with long intervals of horrible insanity.”— Edgar Poe (c.1845)
“Men have called me mad; but the question is not settled, whether madness is or is not the loftiest of intelligence.”— Edgar Poe (c.1845)
“For over two thousand years some subtle relationship has been thought to exist between genius and insanity.”— Bernard Hollander (1921), preface to John Nisbet’s The Insanity of Genius 
“Insanity: doing the same thing over and over again and expecting different results.”— Albert Einstein (c.1930)
“Genius is more often found in a cracked pot than in a whole one.”— E.B. White (c.1950) (Ѻ)
“The sign of a half-baked speculator in the social sciences is his search for something in the social system that corresponds to the physicist's notion of entropy.”— Paul Samuelson (1972) 
1. Schopenhauer, Arthur. (1939). Essay on the Freedom of the Will (pgs. 85-86). Dover, 2005.
2. Nisbet, John F. (1891). The Insanity of Genius (quote, pg. v). Charles Scribner’s Sons, 1921.
3. Samuelson, Paul. (1972). The Collected Scientific Papers, Volume 3 (editor: R. Merton) (pg. 450). Vol. 3. Cambridge, Mass.: MIT Press.
4. Rao, Y.V.C. (2004). An Introduction to Thermodynamics (pg. 98). University Press.
5. Weinhold, Frank. (2009). Classical and Geometrical Theory of Chemical and Phase Thermodynamics (pg. 70). Wiley-Interscience.
6. Baeyer, Hans C. (1998). Warmth Disperses and Time Passes – the History of Heat, (pgs. 101, 110-11). New York: Modern Library.
7. Pirsig, Robert M. (1991). Lila: An Inquiry into Morals (insanity, 13+ pgs). Random House.