Jang Yeong-sil was basically the Elon Musk of Joseon except he actually built everything himself

Here's what blows my mind about Jang Yeong-sil. He was born into the slave class — the absolute bottom of Joseon's rigid social hierarchy. In a society where your birth determined everything, this man had zero chance of becoming anything. But King Sejong noticed his talent and fought his entire court to promote a slave to a government position. The aristocrats were furious. "A slave? Working alongside us?" Sejong basically told them to deal with it. And then Jang Yeong-sil proceeded to invent: a self-striking water clock (Jagyeongnu), a rain gauge (literally the world's first standardized one — 200 years before Europe), a portable sundial, an improved printing press, and astronomical instruments that mapped the Korean sky. All of this in the 1400s. From a slave. With no formal education. The tragic ending? He was eventually stripped of his rank because a sedan chair he built for the king broke. One mechanical failure erased everything. We don't even know when or how he died. The records just... stop. Peak "the system wasn't built for people like him but he broke through anyway" energy.