Laurel water is distilled from the fresh leaves of the cherry laurel, and contains the poison prussic acid (hydrocyanic acid), along with other products carried over in the process.
Pharmacological usage
The water (Latin aqua laurocerasi) has been used for asthma, coughs, indigestion and dyspepsia, and as a sedative narcotic, but since it is effectively a solution of hydrogen cyanide, of uncertain strength, it would be extremely dangerous to attempt medication with laurel water. The Roman emperor Nero used cherry laurel water to poison the wells of his enemies.
References
Laurel water Wikipedia(Text) CC BY-SA