This section is from the book "The Manufacture Of Liquors, Wines, And Cordials, Without The Aid Of Distillation", by Pierre Lacour. Also available from Amazon: Manufacture of Liquors, Wines, and Cordials, Without the Aid of Distillation.
For increasing liquor as above, take from the barrel the per centage of liquor desired, and add a corresponding per centage of clean clear water, charged with a tincture of Guinea pepper (see Formula), and then put on a good bead (see Formula for Bead Bearing). The quantity of pepper can be varied in the above formula, and if the operator desires that the spirit in question should have greater strength (to the taste) than it had previous to the adulteration, it can be obtained by increasing the quantity of pepper, and by the addition of three to four ounces pellitory, well washed, or bruised, to the gallon tincture of pepper.
As the pepper is liable to vary in strength, from age, and unripe seed, and a variety of unexplained causes, the operator will have to depend more upon the judgment of his palate, as to the quantity necessary for any given amount of spirit, and also as to the quantity forming the tincture. For particulars, see Formulas.