Mathematics, such as appertain to painting, are necessary to the painter, also the absence of companions who are alien to his studies: his brain must be versatile and susceptible to the variety of objects which it encounters, and free from distracting cares.

Knowledge of the past and of the places of the earth is the ornament and food of the mind of man.

An artist's studio should be a small space because small rooms discipline the mind and large ones distract it.

Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.

The mind that engages in subjects of too great variety becomes confused and weakened.

It is true that impatience, the mother of stupidity, praises brevity, as if such persons had not life long enough to serve them to acquire a complete knowledge of one single subject, such as the human body; and then they want to comprehend the mind of God in which the universe is included, weighing it minutely and mincing it into infinite parts, as if they had to dissect it!