Scurvy is a potentially fatal illness caused by a lack of vitamin C. Historically it was a problem for sailors, who went out to sea for long periods on a restricted diet. The cure (eating citrus fruit, fresh meat, etc.) has been known since at least the 15th century, but in a tragic comedy of errors this fact was repeatedly forgotten, misapplied, or misunderstood. It wasn’t until 1932 that vitamin C was identified and definitively shown to be the “cure” for scurvy. The linked article explains the long history, with special emphasis on Robert Falcon Scott’s disastrous Terra Nova Expedition to the South Pole.