Thomas Jefferson, to John Adams, 1803

"It is too late in the day for men of sincerity to pretend they believe in the Platonic mysticisms that three are one, and one is three; and yet that the one is not three, and the three are not one. But this constitutes the craft, the power and the profit of the priests."

Thomas Jefferson to John Adams, August 22, 1813

Transcript at The Library of Congress
Scanned letter at The Library of Congress