The motive power is the cause of all life.

Lying on a feather mattress or quilt will not bring you renown.

He who cannot establish dominion over himself will have no dominion over others.

To me it seems that those sciences are vain and full of error which are not born of experience, mother of all certainty, first-hand experience which in its origins, or means, or end has passed through one of the five senses.

A bird maintains itself in the air by imperceptible balancing, when near to the mountains or lofty ocean crags; it does this by means of the curves of the winds which as they strike against these projections, being forced to preserve their first impetus bend their straight course towards the sky with divers revolutions, at the beginning of which the birds come to a stop with their wings open, receiving underneath themselves the continual buffetings of the reflex courses of the winds.

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

Of the four elements water is the second in weight and the second in respect of mobility. It is never at rest until it unites with the sea.