A bird is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements, but not with a corresponding degree of strength, though it is deficient only in the power of maintaining equilibrium. We may therefore say that such an instrument constructed by man is lacking in nothing except the life of the bird, and this life must needs be supplied from that of man.
Leonardo da VinciIt reflects no great honor on a painter to be able to execute only one thing well -- such as a head, an academy figure, or draperies, animals, landscapes, or the like -- in other words, confining himself to some particular object of study. This is so because there is scarcely a person so devoid of genius as to fail of success if he applies himself earnestly to one branch of study and practices it continually.
Leonardo da Vinci