In 1905, the Cullinan Diamond (the largest, gem-quality rough diamond ever found) was supposedly sent from South Africa to the United Kingdom by a heavily guarded steamboat. In actuality, they mailed it in a plain box using registered post. – WTF Fun Facts
Source: https://en.wikipedia.org/wiki/Cullinan_Diamond#cite_ref-8
WTF Fun Fact – Mailed Diamond
