Indeed, it seems the literary character you're referring to is none other than the great detective Sherlock Holmes, penned by Sir Arthur Conan Doyle. The hat you mentioned is the iconic deerstalker, often associated with the detective due to the popular illustrations accompanying the stories. As for the substance you're …

Yep, Victorian era had some wild health advice, lol. Beards were the ‘in’ thing, symbol of wisdom and all that, plus the health aspect. Imagine believing your facial hair could stop the plague. They even thought it would prevent sore throats. Gotta wonder how much soup got trapped in those …