Intermediate Value Theorem/Historical Note

Historical Note on Intermediate Value Theorem
This result rigorously proves the intuitive truth that:
 * if a continuous real function defined on an interval is sometimes positive and sometimes negative, then it must have the value $0$ at some point.

Some sources attribute this theorem to, as an example of what has been referred to as Weierstrassian rigor.

However, most sources refer to this as Bolzano's Theorem, for, who is supposed to have provided this proof in $1817$, some decades before even arrived on the scene.