“You will see,” said Winslow Homer, “in the future I will live by my watercolors.” Homer’s scenes and landscapes capture a rustic America at a time of both expansionism and a turn toward leisure. Born in Boston in 1836, and raised across the river in Cambridge, Massachusetts, he began his career as an illustrator, but after coming back from the Civil War, where he sketched battles, he began to paint. A decade later, Homer took up watercolors as well. Known for his love of maritime subjects, there’s a rightness in that. The medium allowed him to capture volatile waves and shimmering freshwater with powerful immediacy. Today the MFA, Boston, holds the largest collection of Homer’s watercolors in the world. They are fragile, however, and are shown rarely. This winter, the museum presents dozens of them alongside Homer’s related works in other mediums. —Maggie Turner