I say that in narrative paintings one should mingle direct contraries close by, because they produce strong contrasts with one another, and all the more so when they are very close together; that is, the ugly next to the beautiful, the big to the small, the old to the young, the strong to the weak; in this way you will vary as much as possible and close by.
Leonardo da VinciA 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 Vinci