Carl Friedrich Gauss, often rated the greatest mathematician of all time, played the market. On a salary of 1,000 thalers a year, **Euler** left an estate of 170,587 thalers in cash and securities. Nothing is known of Gauss's investment methods.

— Part Three, Arbitrage, This Is Not the Time To Buy Stocks, p. 132

Je voulus faire un jet d’eau dans mon jardin; **Euler** calcula l’effort des roues pour faire monter l’eau dans un bassin, d’où elle devait retomber par des canaux, afin de jaillir à Sans-Souci. Mon moulin a été exécuté géométriquement, et il n’a pu élever une goutte d’eau à cinquante pas du bassin. Vanité des vanités! vanité de la géométrie!

— 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!

Letter H 7434 from Frederick to Voltaire (1778-01-25)

There is a famous formula, perhaps the most compact and famous of all formulas developed by **Euler** from a discovery of de Moivre: It appeals equally to the mystic, the scientist, the philosopher, the mathematician.

— Edward Kasner and James R. Newman, in

One of the most frequently mentioned equations was **Euler** 's equation, Respondents called it "the most profound mathematical statement ever written"; "uncanny and sublime"; "filled with cosmic beauty "; and " mind -blowing". Another asked: "What could be more mystical than an imaginary number interacting with real numbers to produce nothing ?" The equation contains nine basic concepts of mathematics once and only once in a single expression. These are: e (the base of natural logarithms); the exponent operation; ?; plus (or minus, depending on how you write it); multiplication; imaginary numbers; equals; one; and zero.

— Robert P. Crease, in "The greatest equations ever" at PhysicsWeb (October 2004)

There is a famous formula, perhaps the most compact and famous of all formulas developed by **Euler** from a discovery of de Moivre: It appeals equally to the mystic , the scientist , the philosopher , the mathematician .

— Edward Kasner and James R. Newman in

**Euler** calculated the force of the wheels necessary to raise the water in a reservoir … My mill was carried out geometrically and could not raise a drop of water fifty yards from the reservoir. Vanity of vanities! Vanity of geometry!

— Frederick the Great,