 Suppose I said that the eminent Clavius with his own head is a Janus with two heads, would anyone believe me? Suppose that a father common to you and me, were to leave you in his testament two parcels of arable lands, the ones that are two right angles, and made me the executor, would you be satisfied if I gave you the equivalent of the land represented by angle ACF  [figure 1],  which according to Proclus’ demonstration equals two right angles? But on the other hand, we would have to consider this, for the question is one of geometry, which is to say, of measuring the land. (LC: 301: #12, my emphasis)