The Code of the Woosters, chapter 13, Bertie's room at Totleigh, night, moments later
Jeeves says 'Eureka' and recommends dropping the helmet out of the window as footsteps approach.
The text is on its way.
Present: Bertie Wooster, Jeeves
Also there: Oates's helmet
Mentioned: Archimedes, Sir Watkyn Bassett