“To all the Callahan's Places there ever were or ever will be, whatever they may be called — and to all the merry maniacs and happy fools who are fortunate enough to stumble into one: may none of them arrive too late!”

Source: The World We Want (2000), Chapter 3, Virtues And Vices, p. 77.

Fortunate Fool.
Song lyrics, Brushfire Fairytales (2001)

Tales iii, "The Gentleman Farmer".
Tales in Verse (1812)

Book Two, Part I “In the Wilderness”, Chapter 2 (p. 240)
Quest for the White Witch (1978)

"Prescience" <!-- p. 18 -->
The Janitor's Boy And Other Poems (1924)
Context: p>A precious place is Paradise and none may know its worth,
But Eden ever longeth for the knicknacks of the earth.The angels grow quite wistful over worldly things below;
They hear the hurdy-gurdies in the Candle Makers Row.They listen for the laughter from the antics of the earth;
They lower pails from heaven's walls to catch the milk-maids mirth.</p

Source: The Ideological Origins of the American Revolution (1967), Chapter I, THE LITERATURE OF REVOLUTION, p. 1.

The Song of Sixteen, l. 1-4.
Ballads for the Times (1851)

XII, 10.
Epigrams (c. 80 – 104 AD)

Source: Autobiography of Mark Twain, Vol. 2 (2013), p. 239