A company that barely traded anything became Britain's hottest stock, then collapsed
The South Sea Company was granted a monopoly on British trade with Spanish America in 1711 but did very little actual trading. In 1720, it took over a chunk of British government debt in exchange for stock, and speculative buying sent its share price up roughly tenfold in six months before it crashed back down, ruining thousands of investors, including Isaac Newton, who later said he could calculate the motions of planets but not the madness of people.