“The truth of things is the chief nutriment of superior intellects. Science is the captain, and practice the soldiers. Simplicity is the ultimate sophistication.”

“There is no object so large but that at a great distance from the eye it does not appear smaller than a smaller object near. He who is fixed to a star does not change his mind.”

“Water is driving force of all nature. To such an extent does nature delight and abound in variety that among her trees there is not one plant to be found which is exactly like another; and not only among the plants, but among the boughs, the leaves and the fruits, you will not find one which is exactly similar to another. Nature is the source of all true knowledge. She has her own logic, her own laws, she has no effect without cause nor invention without necessity. Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature because in her inventions nothing is lacking, and nothing is superfluous.”

“Why does the eye see a thing more clearly in dreams than the imagination when awake? The senses are of the earth, the reason stands apart from them in contemplation. Common Sense is that which judges the things given to it by other senses.”

“The divisions of Perspective are 3, as used in drawing; of these, the first includes the diminution in size of opaque objects; the second treats of the diminution and loss of outline in such opaque objects; the third, of the diminution and loss of colour at long distances. Painting is concerned with all the 10 attributes of sight; which are: Darkness, Light, Solidity and Colour, Form and Position, Distance and Propinquity, Motion and Rest. The mind of the painter must resemble a mirror, which always takes the colour of the object it reflects and is completely occupied by the images of as many objects as are in front of it. Where the spirit does not work with the hand, there is no art. Our body is dependant on Heaven and Heaven on the Spirit. I have offended God and mankind because my work didn’t reach the quality it should have. For, verily, great love springs from great knowledge of the beloved object, and if you little know it, you will be able to love it only little or not at all. Art is never finished, only abandoned. A beautiful body perishes, but a work of art never dies. Nature never breaks her own laws. Beyond a doubt truth bears the same relation to falsehood as light to darkness.”

“Smallest feline is a masterpiece. The human foot is a masterpiece of engineering and a work of art. The poet ranks far below the painter in the representation of visible things, and far below the musician in that of invisible things. Intellectual passion drives out sensuality. Men of lofty genius, when they are doing the least work are most active.”

“Medicine is the restoration of discordant elements; sickness is the discord of the elements infused into the living body. Tears come from the heart, not the brain. Where there is shouting, there’s no true knowledge. Blinding ignorance does mislead us. Knowledge of the past and of the places of the earth is the ornament and food of the mind of man. The natural desire of a good man is knowledge. O! Wretched mortals, open your eyes!”

“Just as food eaten without appetite is a tedious nourishment, so does study without zeal damage the memory by not assimilating what it absorbs. There are three classes of people: those who see, those who see when they are shown, those who do not see. The noblest pleasure is the joy of understanding. Nothing strengthens authority so much as silence.”

“Iron rusts from disuse; water loses its purity from stagnation… even so does inaction sap the vigor of the mind. I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do. All knowledge which ends in words will die as quickly as it came to life, with the exception of the written word: which is its mechanical part.”

“The spirit desires to remain with its body, because, without the organic instruments of that body, it can neither act, nor feel anything. The human bird shall take his first flight, filling the world with amazement, all writings with his fame, and bringing eternal glory to the nest whence he sprang. I have always felt it is my destiny to build a machine that would allow man to fly. In order to arrive at knowledge of the motions of birds in the air, it is first necessary to acquire knowledge of the winds, which we will prove by the motions of water in itself, and this knowledge will be a step enabling us to arrive at the knowledge of beings that fly between the air and the wind.”

“It seems that it had been destined before that I should occupy myself so thoroughly with the vulture, for it comes to my mind as a very early memory, when I was still in the cradle, a vulture came down to me, he opened my mouth with his tail and struck me a few times with his tail against my lips. I love those who can smile in trouble, who can gather strength from distress, and grow brave by reflection. ‘Tis the business of little minds to shrink, but they whose heart is firm, and whose conscience approves their conduct, will pursue their principles unto death. While I thought I was learning how to live, I have been learning how to die.
Learning never exhausts the mind. Life well spent is long.”

Poor is the pupil who does not surpass his master.