seat of ease
n.— «Taking medicine meant swallowing improbable quantities of calomel, suphur, Turkey rhubarb (often added to their own surgeon’s prescription) and spending the whole of the next day on the seat of ease, gasping, straining, sweating, ruining their lower alimentary tract.» —by Patrick O’Brian The Truelove May 1, 1992. (source: Double-Tongued Dictionary)