King Yeongjo had his own heir sealed in a rice chest — and broke his succession

King Yeongjo, the twenty-first ruler of Joseon, took the throne under a cloud of disputed legitimacy, and his long reign was defined by factional strife between the Noron and Soron camps. His heir was his second son, Crown Prince Sado, born in 1735 and invested as successor. From 1749 the prince handled regency duties, but the king's harsh and repeated berating — and repeated accusations from the Noron faction — wore him down; in 1761 a memorial listed ten counts of the prince's misconduct.

In 1762 Yeongjo decided to kill the heir, as he put it, for the nation's future. He first ordered Sado to take his own life; when the prince refused, the king deposed him to commoner rank and had him sealed inside a wooden rice chest. After eight days he was found dead, and he received the posthumous name Sado. By one contemporary account, the king never expressed sorrow for the act.

The succession then had to be rebuilt around the act that was meant to protect it. Yeongjo kept Sado's son Yi San as heir, but forced the boy to disown his dead father and be registered as the son of the king's own deceased first son. Yi San became King Jeongjo in 1776, fourteen years after his father's death, and reigned under the shadow of a condemned father; he later restored Sado's honour. The 'solution' generated decades of fresh factional argument over whether the prince had been innocent.