The simile seems hardly worthy of the topic.  The practice is referred to by Plutarch, Symp. Quæst. i. 9, and by Pliny, Hist. Nat. ii. 106.  “Omne oleo tranquillari; et ob id urinantes ore spargere, quoniam mitiget naturam asperam lucemque deportet.”  “gerere” says the Delph. note, “tum credas oleum vicem conspiciliorum.