text: Qin Shi Huang also followed the theory of the five elements: fire, water, earth, wood, and metal. () It was believed that the royal house of the previous dynasty Zhou had ruled by the power of fire, associated with the colour red. The new Qin dynasty must be ruled by the next element on the list, which is water, Zhao Zheng's birth element. Water was represented by the colour black, and black became the preferred colour for Qin garments, flags, and pennants. Other associations include north as the cardinal direction, the winter season and the number six. Tallies and official hats were  long, carriages  wide, one pace () was .
  Third assassination attempt
  In 230 BC, the state of Qin had defeated the state of Han. In 218 BC, a former Han aristocrat named Zhang Liang swore revenge on Qin Shi Huang. He sold his valuables and hired a strongman assassin, building a heavy metal cone weighing 120 jin (roughly 160 lb or 97 kg). The two men hid among the bushes along the emperor's route over a mountain during Qin Shi Huangdi's third imperial tour. At a signal, the muscular assassin hurled the cone at the first carriage and shattered it. However, the emperor was travelling with two identical carriages to baffle attackers, and he was actually in the second carriage. Thus the attempt failed, though both men were able to escape the subsequent manhunt.
  Public works
  Great Wall
  Numerous state walls had been built during the previous four centuries, many of them closing gaps between river defences and impassable cliffs. To impose centralized rule and prevent the resurgence of feudal lords, the Emperor ordered the destruction of walls between the former states, which were now internal walls dividing the empire.