Thoreau writes in his journal:
9 A.M.—Start to get two quarts of white maple sap and home at 11.30 . . .
You bore a little hole with your knife, and presently the wounded sap-wood begins to glisten with moisture, and anon a clear crystalline tear-like drop flows out and runs down the bark, or drops at once to the snow. This is the sap of which the far-famed maple-sugar is made. That’s the sweet liquor which the Indians boiled a thousand years ago . . .