Jang Yeong-sil was a SLAVE who became Joseon's top scientist. Then they threw him away.

Born into the lowest social class, Jang Yeong-sil was so brilliant that King Sejong personally freed him and put him in charge of the royal science bureau. He invented the rain gauge (first in the world btw), water clocks, sundials, astronomical instruments — basically Joseon's entire scientific revolution was this one dude. Then in 1442, a royal sedan chair he designed broke while carrying the king. He was arrested, flogged, and stripped of his rank. We literally don't know what happened to him after that. History just... forgot him.