This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Take of good fresh ground hops one pound, diluted alcohol sufficient to make the desired quantity of extract. Moisten the hops and pack in percolator, then add enough diluted alcohol to cover the hops and leave a stratum above. Close the percolator and macerate for forty-eight hours. Then proceed to percolate. Add sufficient diluted alcohol until sixteen fluid ounces of extract or any other desired quantity is obtained.