Coleus is a plant with poisonous leaves. It is unknown if the leaves are poisons before the drying process.
In The Queen of Attolia, Attolia gradually gathers coleus leaves in secret and dries them, before making them into a powder. Aware that her new husband was boorish enough to drink from her wine glass without asking her, she places coleus powder into her wine during their wedding feast. Her husband dies soon after drinking the wine from her cup. The incident becomes infamous and the court knows never to drink from the queen's glass.