Aunt Jane's Nieces at Millville by L. Frank Baum

Ethel Thompson came over the next day, as she had promised, and the sweet-faced, gentle school-mistress won the hearts of Uncle John's three nieces without an effort. She was the eldest of them all, but her retired country life had kept her fresh and natural, and Ethel seemed no more mature than the younger girls except in a certain gravity that early responsibility had thrust upon her.

Together the four laughing, light-hearted maids wandered through the pines, where the little school-ma'am showed them many pretty nooks and mossy banks that the others had not yet discovered. By following an unsuspected path, they cut across the wooded hills to the waterfall, where Little Bill Creek made a plunge of twenty feet into a rocky basin below. In spite of the bubbles, the water here showed clear as crystal, and the girls admiringly christened it the "Champagne Cup. " They shed their shoes and stockings and waded in the pool, enjoying the sport with shrieks of merry laughter -- more because they were happy than that there was anything to laugh at.