But Honest Abe wasn't always so serene. During his failed campaign for Illinois' Senate seat in the late 1850s, friends reported that he suffered explosive and unexplained fits of rage. On one occasion, the soon-to-be president is alleged to have grabbed a fellow politician and shaken him "until his teeth chattered." Now, British scientists say they have identified the cause of this un-Lincolnesque behavior: exceptionally high levels of mercury in tablets he took for constipation.
Researchers at the Royal Society of Chemistry recently uncovered several of these little blue pills -- popularly called "Blue Mass" -- in a museum in Devon County, England. Lincoln's law partner and biographer, William H. Herndon, was among the contemporaries who said that Lincoln took the pills, which were widely used in the mid-19th century to treat everything from toothache and bowel troubles to depression.
The chemists' analysis of the tablets revealed that if Lincoln followed common practice and took two or three pills a day, he would have ingested 80 to 120 times the World Health Organization's acceptable daily intake of mercury.
This highly toxic dosage could explain Lincoln's uncharacteristic outbursts, as symptoms of mercury poisoning include sudden violent mood changes as well as nausea, insomnia and depression.
"To think that the president was meant to be taking two of them a day is appalling," said Dr. Bin Chen, who carried out the test.
Reports by Herndon and others suggest that Lincoln first started popping "Blue Mass" around 1858 and quit at the beginning of 1860, shortly before the Republican Party nominated him for the presidency. But James Cornelius, curator of the Lincoln Collection at the Abraham Lincoln Presidential Library in Springfield, Ill., says that because the president didn't keep a diary, it's almost impossible to tell how long he took them for, or how many he popped a day.
Cornelius adds that the late 1850s were a tense time for Lincoln, so it's possible his foul mood was caused by any number of stresses. He points out that "arguably the biggest event of his life" -- a series of seven debates with Stephen A. Douglas, his rival in the Illinois Senate race -- took place in 1858, the year when Lincoln allegedly suffered most of his bad tempers.
"It was a grueling, long, hot, dusty summer," Cornelius says. "So while it's possible that he was taking these pills on the road, these supposed outbursts of anger might just as well have been triggered by the heat of the debates, the exhausting schedule and the importance of the political issues. They were essentially fighting about whether slavery should continue to expand in the U.S."
However, Cornelius suspects that the little blue pills did play a significant role in his rages. "What's remarkable about Lincoln -- and people said this all up and down the line -- is that he never took personal offense at his enemies," he says. "So if there's even a single example of him getting angry with somebody and getting into a shouting match, then it looks like [these pills] would be among the likelier explanations. Because he just didn't lose his temper."
After quitting the pills, that cool demeanor quickly returned. Cornelius says Lincoln likely dumped the pills around January 1860, a month before he was due to give a speech to a group of Republican high-ups at New York's Cooper Union. That oration was intended to show that an almost unknown Westerner with no formal education could head the country as well as any Easterner.
"He suspected that this would be the biggest speech of his career," says Cornelius. "He would have been focused like never before on making a good appearance. And if he had a sense that these medications were not doing him good, he would have stopped taking them before heading off on that trip."
The pill-free Lincoln wowed his audience, proving himself to be composed, intelligent and dignified, and a better prospective leader than New York's own Sen. William Henry Seward. Lincoln was picked as the Republicans' presidential candidate three months later. And in November 1860, the American people chose that coolheaded lawyer as their new president.