Emperor Xuanzong of Tang (9th century)

When the emperors visited the imperial princes' residences, known as the Sixteen Mansions, they would, as a game, try to get Li Yi to speak, and they referred to him as "Uncle Guang."

The palace eunuchs gathered and decided on Li Yi as Emperor Wuzong's successor, probably because they considered him simple-minded and therefore easier to control.

It was said that when Li Chen met the officials in his new role as crown prince, they were astonished that the apparent simpleton exhibited punctilious adherence to the complex ritual expressions of grief for Wuzong, and immediate knowledgeable management of the court's pending business.

[2][8][9] A number of policies that Emperor Wuzong and Li Deyu had pursued, including persecution against Buddhism and alliance with the Yenisei Kirghiz, were reversed.

[8] Meanwhile, Emperor Xuanzong also turned his attention to the Tibetan Empire, which had fallen into intense civil war after the death of its king Langdarma in 842.

[10] Starting in 848, and over a period of several years, Emperor Xuanzong commissioned border troops to recapture various prefectures lost to the Tibetan Empire since the An Lushan Rebellion, taking the region constituting modern eastern Gansu, southern Ningxia, and western Sichuan.

[2][8] He also encouraged frugality, and tried to demonstrate it by reducing the expenditures for the wedding of his favorite daughter Princess Wanshou to the imperial official Zheng Hao (鄭顥).

)[2] One of the major themes later in Emperor Xuanzong's reign was the high-level officials' concerns that he was not creating a Crown Prince, as this refusal to do so left the imperial succession uncertain.

[8] Late in Emperor Xuanzong's reign, he came to favor certain alchemists who had promised him immortality, taking regularly the cinnabar-based pills which they manufactured and prescribed.

It was said that as a result of poisoning by these pills, he became paranoid and easily angered, and by 859, as a further side effect of the consumption of these toxic, mercurial elixirs, he had developed a large ulcerous boil on his back, rendering him bedridden and unable to conduct meetings with his chancellors and other officials.

[8] During Sulaiman al-Tajir's stay at the city of Guangzhou he noted that the Chinese used fingerprint records to maintain the identities of newly arrived foreigners and charged extortionate rates for imported goods, and that the route to China by sea was dangerous due to piracy and frequent rain.

Because of the prosperity of Emperor Xuanzong's reign, it was said that in subsequent years, including after Tang's eventual fall in 907, the people missed him bitterly, referring to him as "Little Taizong.

[3] The lead editor of the New Book of Tang, Ouyang Xiu, however, commented that Emperor Xuanzong, while having good judgment, lacked kindness or grace.

[15] Played by Moses Chan, a fictionalized version of Xuanzong was portrayed in 2009 Hong Kong's TVB television series, Beyond the Realm of Conscience.