“Think nothing outside their paper.”

Speech to Chamber of Deputies (9 December 1928), quoted in Propaganda and Dictatorship (2007) by Marx Fritz Morstein, p. 48
1920s

Source: Phenomenology of Perception

According to The quote verifier: who said what, where, and when (2006), Keyes, Macmillan, p. 91 ISBN 0312340044 , the cover of a trade magazine once credited this observation to Churchill, but it dates back well into the nineteenth century, and has been variously attributed to Henry Ward Beecher, Oliver Wendell Holmes, w:Theodore Roosevelt, w:Thomas Jefferson, w:Will Rogers and Lord Palmerston, among others. One documented use in Social Silhouettes (1906) by George William Erskine Russell, p. 218 wherein a character attributes the saying to Lord Palmerston.
Misattributed

Source: Flatland: A Romance of Many Dimensions (1884), PART II: OTHER WORLDS, Chapter 18. How I came to Spaceland, and What I Saw There
Context: I could see many of the younger Counsellors start back in manifest horror, as the Sphere's circular section widened before them. But on a sign from the presiding Circle — who shewed not the slightest alarm or surprise — six Isosceles of a low type from six different quarters rushed upon the Sphere. "We have him," they cried; "No; yes; we have him still! he's going! he's gone!" "My Lords," said the President to the Junior Circles of the Council, "there is not the slightest need for surprise; the secret archives, to which I alone have access, tell me that a similar occurrence happened on the last two millennial commencements. You will, of course, say nothing of these trifles outside the Cabinet."

Cause, Principle, and Unity (1584)

Source: 1Q84

Introduction, p. vii.
On Writing Well (Fifth Edition, orig. pub. 1976)