I started reading The Sixth Extinction: An Unnatural History by Elizabeth Kolbert. In the second chapter, she writes of mastodon bones discovered in Kentucky in 1739. No one knew what they were for a while, and one European doctor called the animal the incognitum. And this is where psycho Thomas Jefferson comes in.
Jefferson concocted his own version of the incognitum. The animal was...the largest of all beasts--"five or six times the cubic volume of the elephant."...The creature...was probably carnivorous. But it was still out there somewhere. If it could not be found in Virginia, it was roaming those parts of the continent that "remain in their aboriginal state, unexplored and undisturbed." When, as president, he dispatched Meriwether Lewis and William Clark to the Northwest, Jefferson hoped that they would come upon live incognita roaming its forests. [p. 27]
Say what? Jefferson thought there was a carnivorous animal six times the size of an elephant and he sent Lewis and Clark to GO BE EATEN BY IT. That is some straight-up psychopathic scientific discovery. Imagine his disappointment when they returned.