This section is from the book "A Practitioner's Handbook Of Materia Medica And Therapeutics", by Thos. S. Blair. Also available from Amazon: A Practitioner's handbook of Materia Medica and Therapeutics.
Marrubium, Hoarhound. A mild expectorant used principally in the form of a syrup. Macerate an ounce of the dried herb for three hours in 1/2 pint of boiling water, strain, and add water sufficient to make 1/2 pint infusion; add I pound of sugar. This makes an agreeable syrup, suitable as a vehicle for any indicated active expectorant.