definitely, deadly nightshade!

The Deadly Nightshade of Hampton Court! The common name belladonna originates from its historic use by women - Bella Donna is Italian for beautiful lady.  Drops prepared from the belladonna plant were used to dilate  women's pupils, an effect considered attractive.  Belladonna is currently rarely used cosmetically, as it carries the adverse effects of causing minor visual distortions, inability to focus on near objects, and increased heart rate.  Prolonged usage was reputed to cause blindness.
A. belladonna, the berries of belladonna, has been used in traditional treatments  for centuries for an assortment of conditions including headache, menstrual symptoms, peptic ulcer disease, histaminic reaction, inflammation, and motion sickness, with at least one 19th century eclectic medicine journal explaining how to prepare a Belladonna tincture for direct administration to patients.  Homeopathic belladonna preparations have been sold as treatments for various conditions, although there is no scientific evidence to support their efficacy.

The Deadly Nightshade's poison was used by early men in poisonous arrows.  In Ancient Rome, it was used as a poison by Agrippina the younger, wife of Emperor Claudius, and Livia,  who is rumored to have used it to kill her husband Emperor Augustus.  Macbeth of Scotland, when he was still one of the lieutenants of King Duncan I of Scotland, used it during a truce to poison the troops of the invading Harold Harefoot, King of England, to the point that the English troops were unable to stand their ground and had to retreat to their ships.  The leaves of belladonna, in the past, it was believed that witches used a mixture of belladonna, opium poppy and other plants, typically poisonous  in flying ointment they applied to help them fly to gatherings with other witches.   But Carlo Ginzburg and others have argued that flying ointments were preparations meant to encourage hallucinatory dreaming.