Philo of Byzantium was a Greek engineer born around 250 BC. He wrote one of the earliest textbooks on mechanics. Although mentioned briefly by both Vitruvius and Hero, little is known about Philo other than what is gleaned from the surviving fragments of his great book. He was apparently supported by a wealthy patron, Ariston, to whom each extant section of his book was dedicated. Philo's book probably consisted of nine chapters that discussed the lever, the construction of seaports and fortresses, catapults, pneumatics, automatic theaters, and military tactics. Only three chapters survive.