in Thoreau’s Journal:

There are some fine large clusters of lambkill close to the shore of Walden and in the Peak fronting the south–– They are early there & large ap. both on account of the warmth & the vicinity of the water –– These flowers are in perfect cylinders sometimes 6 inches long by 2 wide––and 3 such raying out or upward from one centre i.e. 3 branches clustered together.

Examined closely I think this handsomer than the mt. Laurel which we have.  The color is richer––but they do not show so well at a little distance and the corymbs are somewhat concealed by the green shoot and leaves rising above them, and also injured by the mixture of the dry remains of last years flowers––