In 1942 Niels Bohr was asked to give an address on the 300th anniversary of Isaac Newton’s birth. In discussing with Abraham Pais the themes that he might address, he wrote the word harmony on a blackboard:

As they continued to talk he grew dissatisfied with this. At last he said, “Now I’ve got it. We must change harmony to uniformity.” And he did so with “one triumphant bang”:

Pais called this “the most remarkable act of calligraphy I shall ever witness.”

See Letter From New York.