“The art of the parenthesis is one of the great secrets of eloquence in Society.”

Bartlett's Familiar Quotations, 10th ed. (1919), Journal

Canto III, stanza 22.
The Corsair (1814)

Part III, Section XXIX
Christian Morals (first pub. post. 1716)

toke.c
Source code, Other files

Four VII
is 5 (1926)

Interview with Alex Haley

Address to Polaroid employees at Symphony Hall in Boston, Massachusetts (5 February 1960), as quoted in Insisting on the Impossible : The Life of Edwin Land (1998) by Victor K. McElheny, p. 7
Land was not the first to make such observations; in One Man in His Time (1922), p. 162, Ellen Glasgow has a character state:
Half the time when he is telling the truth, it sounds like a joke, and that keeps people from believing him. He says the best way to keep a secret is to shout it from the housetops; and I've heard him say things straight out that sounded so far fetched nobody would think he was in earnest. I was the only person who knew that he was speaking the truth.

1961, Address to ANPA
Context: The very word "secrecy" is repugnant in a free and open society; and we are as a people inherently and historically opposed to secret societies, to secret oaths and to secret proceedings. We decided long ago that the dangers of excessive and unwarranted concealment of pertinent facts far outweighed the dangers which are cited to justify it. Even today, there is little value in opposing the threat of a closed society by imitating its arbitrary restrictions. Even today, there is little value in insuring the survival of our nation if our traditions do not survive with it. And there is very grave danger that an announced need for increased security will be seized upon by those anxious to expand its meaning to the very limits of official censorship and concealment. That I do not intend to permit to the extent that it is in my control. And no official of my Administration, whether his rank is high or low, civilian or military, should interpret my words here tonight as an excuse to censor the news, to stifle dissent, to cover up our mistakes or to withhold from the press and the public the facts they deserve to know.

Se l'arte dell'eloquenza è l'arte di persuadere, non vi è altra eloquenza che quella di dire sempre il vero, il solo vero, il nudo vero. Le parole, onde è necessità di nostra inferma natura di rivestire il pensiero, saranno tanto più potenti, quanto più atte al fine, cioè più nudo lasceranno il vero, che è nel pensiero.
Platone in Italia