Countess Elizabeth Bathory, of Hungarian legend, comes to my mind first. A truly exemplary woman, who took her own fate into her hands. She failed because she didn’t test her methods. She believed bathing in the blood of a virgin woman would keep her eternally young.
She lacked a control test. There are several easy experiments one could have set up, and with modern methods and thinking, I have no doubt she’d have been tireless in her research to find a way.