Buttercup
2 of the 7 encyclopedias on this shelf carry an entry for Buttercup. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a large group of flowering herbs. The Latin name, Ranunculus, little frog, perhaps refers to the wet places in which many kinds grow. Another name, crowfoot, has, no doubt, reference to the shape of the five-toed leaves of the most common species. Buttercup comes from the yellow color and cup-shape of the flower. The English buttercup is the plant children hold under each others' chins to see by the yellow glow "whether they love butter." Buttercups have a simple flower, in that all parts of the flower grow entirely distinct. There are over two hundred kinds. The garden buttercup originated in Asia. Some of our native buttercups are aquatic and have thread-like leaves. The tall buttercup, a visitor from Europe, and a plague in pastures, has established itself in New England and around the western end of Lake Superior. Buttercups are usually yellow--sometimes white. The marsh marigold, virgin's bower , clematis, anemone, pasque flower with its hairy "goslings," columbine, and even the larkspur, all belong to the crowfoot family. 2026 Editor's Note: The chin trick has been explained. A 2011 study found the buttercup petal has a uniquely smooth double layer with an air gap beneath, making it act almost like a mirror — which is why it flashes yellow light under the chin so vividly. The plants are also acrid and mildly toxic, so grazing animals avoid them, which is exactly why buttercups take over an overgrazed field. (Ed: BR 2026-07-05)
Collier's New Encyclopedia (1921)
the popular name of two or three species of the ranunculus, namely, R. acris, R. bulbōsus, and R. repens. They are common plants with yellow flowers. brilliant