In 1870, the German chemist Erich von Wolf was investigating the amount of iron in spinach. When writing down his findings in his notebook, he misplaced a decimal point, changing the iron content in spinach ten times more than in reality. While Mr. von Wolf found out that there are just 3.5 milligrams of iron in a 100g serving of spinach, the published number became 35 milligrams thanks to his mistake. This caused the well-known misconception that iron is exceptionally high in spinach, which makes the body stronger. 

Though Mr. von Wolf's error was detected and fixed 67 years later when someone re-checked his results, spinach is still popularly thought to be one of the most iron-rich vegetables, probably due to the popular cartoon character Popeye.