As the days went by and he waited for commissions to come, Leonardo took to wandering about the streets of Rome. He stood in the half-buried Forum of the Caesars surrounded by grazing sheep and grunting pigs. Wooden shacks where crude cartwheels were made and where the marble from the ancient temples was cut and sold, were built against the sides of crumbling ruins. The old triumphal arches, now overgrown with creepers, were boarded into towers and cattle were penned between the shafts of columns that once supported the grandeur of temple roofs. Here and there a classical scholar would be sketching or writing from the worn, Latin inscriptions on a marble slab tilted crazily from the ground where it had fallen hundreds of years ago. Goats wandered on the Palatine hill, once the home of Emperors, and the great baths of the Emperor Diocletian were now a deer park and a hunting ground for royalty.
During the course of these wanderings, Leonardo became interested in the primitive methods of carpentry. Such things as screws, for example, were rare. Those that were used were either made of wood or, if of metal, by goldsmiths laboriously making each one by hand, soldering wire around a pin and another wire into the hole to hold the screw. Sometimes they were made by filing pieces of metal individually. All these methods were time-consuming and costly.
Leonardo had thought of this problem before, and now he concentrated on perfecting his ideas about it. Previously, he had thought of casting the metal in wooden molds and then turning the metal on thread-cutters. The designs he finally drew in careful detail, however, are essentially the methods used today. The new machines did with a few turns of a handle and adjustments of a few cogged wheels what it took one man many hours to perform. He also drew designs for a mechanical plane and a machine for drawing wire that worked by water power.
Leonardo now lived and worked in the Belvedere of the Vatican—more a man on exhibition than an active participant in the great artistic activities taking place around him. True, he received his thirty-three ducats a month, but Michelangelo had been paid three thousand for his work in the Sistine Chapel, while Raphael had earned twelve thousand for each room he painted in the Vatican.