To tell the truth, in his time, the mausoleum of the First Qin Emperor had been destroyed. The setting in the mausoleum must be false, hearsay, because the people who built the mausoleum of Qin Shihuang are basically dead. But the external basic structure should be true for two reasons:
1, Sima Qian's time is only one hundred years away from Qin Shihuang. The archives of the Central Committee of the Han Dynasty inherited many official documents and materials of the Qin Dynasty. It is entirely possible that the original materials of the Qin Dynasty recorded the specifications of the mausoleum of the First Qin Emperor for future emperors to refer to when building the mausoleum. As an official in charge of these materials, Sima Qian was able to read these files left over from the Qin Dynasty.
2. Sima Qian's academic spirit is rigorous. For uncertain legends, he will explain them in historical records or simply omit them, and never speculate (such as the deeds of the ancient five emperors, the chronology of Xia, Shang and Zhou Dynasties). The description of Qin Shihuang's tomb is so clear that he saw absolutely authoritative and reliable information, which is why he spoke in such detail. Words, should be true.