In honor of President's Day this Monday, we're taking a look back on one of the strangest chapters in Abraham Lincoln's life. Before his inauguration, Lincoln regularly took blue mass, or pills that contained elemental mercury. Although he officially took the pills for his constipation, it's long been thought that Lincoln used blue mass to treat his depression, too. Of course, our 16th president's struggles with mental health feature prominently in accounts of his life — William Herndon, Lincoln's law partner, went so far as to say that "his melancholy dripped from him as he walked." He was said to suffer from depressive episodes and may have even penned a poem called "The Suicide's Soliloquy." If you thought taking blue mercury pills would improve Lincoln's mental health, think again. Reports of Lincoln's temper paint a pretty scary picture: He physically attacked an aide during a debate, shaking the man hard enough that his teeth rattled. Lincoln's friends and political opponents alike witnessed his extreme mood swings. One man described his face during a fit of rage as "lurid with majestic and terrifying wrath." There's no way to know for sure if his moods were a direct result of the mercury, but stories about President Lincoln tell of a even-keeled, thoughtful man, as opposed to the mercurial (pun intended) young lawyer. For what it's worth, Lincoln stopped taking blue mass a few months after his inauguration. As we mentioned earlier, despite its reputation as a cure-all for a lot of history, mercury is bad news. In addition to mood swings, symptoms of chronic or acute mercury exposure can range from headaches and tremors to kidney failure and death. In other words, it's a good thing that Lincoln stopped taking his blue pills when he did. Lucky for him (and the United States), the mild effects of mercury poisoning are usually treatable in adults.