BBB Etymology - Leave no stone unturned

After the defeat of Mardonius at Platæa (B.C. 477), a report was current that the Persian General had left great treasures in his tent. Polycrates (4 syl.) the Theban sought long but found them not. The Oracle of Delphi, being consulted, told him “to leave no stone unturned,” and the treasures were discovered.