"dose of castor-oil"
Castor Oil
Creative Commons AttributionCastor Oil - Credit: Pictures from Heather

Made from the castor bean, castor-oil is a foul-tasting medicinal oil. A popular folk medicine, castor-oil has been known to be used as a threat to children. Certainly there are plenty of children who would rather behave than be administered a dose. 

In Mussolini-controlled Italy, political dissidents were force fed castor-oil, which dehydrated victims.