It is cocaine," he said, "a seven-per-cent solution. Would you
care to try it?"
"No, indeed," I answered brusquely. "My constitution has not got
over the Afghan campaign yet. I cannot afford to throw any extra
strain upon it."
He smiled at my vehemence. "Perhaps you are right, Watson," he
said. "I suppose that its influence is physically a bad one. I find
it, however, so transcendently stimulating and clarifying to the
mind that its secondary action is a matter of small moment.

Author: Arthur Conan Doyle