“Only laughter can blow [a colossal humbug] to rags and atoms at a blast. Against the assault of laughter nothing can stand.”

"The Chronicle of Young Satan" (ca. 1897–1900, unfinished), published posthumously in Mark Twain's Mysterious Stranger Manuscripts (1969), ed. William Merriam Gibson ( pp. 165–166 http://books.google.com/books?id=LDvA2xcYZKcC&pg=PA165 in the 2005 paperback printing, ).
Source: The Mysterious Stranger and Other Curious Tales
Context: Your race, in its poverty, has unquestionably one really effective weapon—laughter. Power, Money, Persuasion, Supplication, Persecution—these can lift at a colossal humbug,—push it a little—crowd it a little—weaken it a little, century by century: but only Laughter can blow it to rags and atoms at a blast. Against the assault of Laughter nothing can stand.

Source: Shōgun

Source: Proven Guilty

From an article in Sovetskoye Iskusstvo, November 5, 1934; translation from Laurel Fay Shostakovich: A Life (2000) p. 77.

Source: The Diary of Frida Kahlo: An Intimate Self-Portrait

"Dedicatory Ode", stanza 22
Verses (1910)
Context: From quiet homes and first beginning,
Out to the undiscovered ends,
There's nothing worth the wear of winning,
But laughter and the love of friends.

Attributed quotes