Hero demolished both his friends and his soldiers, who had helped him in the execution of his plans; he found new friends, and raised other troops. I… - Frederick II of Prussia

I wanted to have a water jet in my garden: Euler calculated the force of the wheels necessary to raise the water to a reservoir, from where it should fall back through channels, finally spurting out in Sans Souci. My mill was carried out geometrically and could not raise a mouthful of water closer than fifty paces from the reservoir. Vanity of vanities! Vanity of geometry!

We humans are foolish in many ways: we want to conquer all as if we had all time, as if our lives did not have any end. Thus, our real time passes too quickly, and often when one believes that they are working only for themselves, they are in fact working for unworthy or ungrateful successors.

But a prince, when he binds himself, does not bind himself alone, otherwise he would be in the same position as a private individual. Instead, he exposes great countries and great provinces to a thousand misfortunes. Therefore, it is better that he should break his contract rather than that the people should perish.