In the Beall-Booth Family papers at the Filson Historical Society there is a description of charcoal mellowing whiskey. It is an undated document, but the paper and similar documents date it to the first 10 years of the 19th century. The document even has a little drawing showing the false bottom and spigot for the whiskey.
Receipt to purify whisky and other Ardent Spirits.
Take a tub of one hundred gallons and put a false Bottom about 8 or 10
inches from the other bottom the false bottom must be full of Holes then
fasten on the top of the false bottom three or four thicknesses of white
flannel then put about three or four inches thick clean white sand then
put about 18 or 20 Inches thick of pulverized charcoal made of good green
wood such as sugar tree Hickory & then fill up the vacancy with whisky
or other ardent spirits take care to pour it up til it becomes perfectly clear
and purified. To make Rum add one to five Brandy one to four or five”
Gary - Any opinions to what he means about the rum or brandy? I assume it means run it through the tub that many more times.