

No known source in Twain's works.
The earliest known source is a Usenet post from November 2000 https://groups.google.com/forum/message/raw?msg=israel.francophones/j_b0peHVcJw/YN5cG6Pdk6QJ.
Disputed
1860s, 1864, Letter to the City of Atlanta (September 1864)
Context: You have heretofore read public sentiment in your newspapers, that live by falsehood and excitement; and the quicker you seek for truth in other quarters, the better. I repeat then that, by the original compact of government, the United States had certain rights in Georgia, which have never been relinquished and never will be; that the South began the war by seizing forts, arsenals, mints, custom-houses, etc., etc., long before Mr. Lincoln was installed, and before the South had one jot or tittle of provocation. I myself have seen in Missouri, Kentucky, Tennessee, and Mississippi, hundreds and thousands of women and children fleeing from your armies and desperadoes, hungry and with bleeding feet. In Memphis, Vicksburg, and Mississippi, we fed thousands and thousands of the families of rebel soldiers left on our hands, and whom we could not see starve. Now that war comes to you, you feel very different. You deprecate its horrors, but did not feel them when you sent car-loads of soldiers and ammunition, and moulded shells and shot, to carry war into Kentucky and Tennessee, to desolate the homes of hundreds and thousands of good people who only asked to live in peace at their old homes, and under the Government of their inheritance. But these comparisons are idle. I want peace, and believe it can only be reached through union and war, and I will ever conduct war with a view to perfect an early success.
No known source in Twain's works.
The earliest known source is a Usenet post from November 2000 https://groups.google.com/forum/message/raw?msg=israel.francophones/j_b0peHVcJw/YN5cG6Pdk6QJ.
Disputed
"Obstacles to Happiness", p. 74
Awareness (1992)
Context: Suffering is a sign that you're out of touch with the truth. Suffering is given to you that you might open your eyes to the truth, that you might understand that there's falsehood somewhere, just as physical pain is given to you so you will understand that there is disease or illness somewhere. Suffering points out that there is falsehood somewhere. Suffering occurs when you clash with reality. When your illusions clash with reality when your falsehoods clash with the truth, then you have suffering. Otherwise there is no suffering.
“Draw from your imagination and read whatever gets you excited.”
John Steven Gurney https://clifonline.org/john-steven-gurney-illustrator-author/ (March 30, 2021)
“The more you read and write, the better you think and live.”
In a letter to his sister, New Year's Day, 1882. Quoted in the Preface
Matthew Arnold's Notebooks (1902)
“Take your Bible and take your newspaper, and read both. But interpret newspapers from your Bible.”
Reporters and editors luncheon address (2007)