The cause of Qin Shi Huang's death is not clearly recorded in the history books, but it is generally believed that he died of illness during the parade. As for the reason why Qin Shi Huang only lived to be 49 years old, there are several possibilities:
1. **Cause of illness**: Long-term exertion and mental stress may have caused Qin Shi Huang's health problems. In ancient times, medical conditions were limited, and once you suffered from a serious illness, it was difficult for you to get effective treatment, even if you were an emperor.
2. **Psychological pressure**: After Qin Shi Huang unified the six countries, the domestic political pressure was huge, coupled with foreign wars and large-scale engineering construction (such as the construction of the Great Wall, Afang Palace, Terracotta Warriors, etc.), which made his psychological pressure extremely great. This long-term mental burden may have affected his physical health.
3. **Assassination or poisoning**: Although historical books such as the Records of the Historian do not explicitly record the assassination of Qin Shi Huang, there is an opinion that Qin Shi Huang may have been poisoned or assassinated by people around him during his parade. This claim is mentioned in some later literature and folklore, but there is a lack of conclusive evidence.
4. **Taking "Yuan Shui"**: The claim that Qin Shi Huang died after taking "Yuan Shui" does not find support in reliable historical documents. The so-called "yuan water" may refer to a certain medicine or elixir, and in ancient times, there were indeed many emperors who sought elixirs, but these drugs were often toxic, and long-term use could harm health and even lead to death.
5. **Overwork**: After the unification of China, Qin Shi Huang carried out a large number of political reforms and construction projects, these activities undoubtedly consumed a lot of physical strength and energy, and long-term overwork may also have contributed to his early death.
In summary, the cause of Qin Shi Huang's death may have been the result of many factors, including illness, psychological stress, and overwork. As for the term "Yuan Shui", it may come from legends or misunderstandings in later generations, and is not direct evidence of the cause of his death. Qin Shi Huang's life is full of legends, and his death is similarly surrounded by legends and speculations, but the exact truth may have been blurred over time.