Leonardo da Vinci (1452–1519) wrote in his notebook titled Facezie e storie that “the virtue of gratitude is said to be more [developed] in the birds called hoopoes which, knowing the benefits of life and food they have received from their parents, when they see them grow old, make a nest for them, feed them, and with their beaks pull out their old and shabby feathers. With a certain herb dropped in their old eyes they restore their sight.”
