From Balzac’s “The Pleasures and Pains of Coffee”:
Coffee affects the diaphragm and the plexus of the stomach, from which it reaches the brain by barely perceptible radiations that escape complete analysis; that aside, we may surmise that our primary nervous flux conducts an electricity emitted by coffee when we drink it. Coffee’s power changes over time. Rossini has personally experienced some of these effects as, of course, have I. “Coffee,” Rossini told me, “is an affair of fifteen or twenty days; just the right amount of time, fortunately, to write an opera.” This is true. But the length of time during which one can enjoy the benefits of coffee can be extended.
This is a great essay with some vivid descriptions of coffee from 1830.