While you have an opportunity in ſhops to ſee compound medicines prepared, you ought carefully to obſerve what proportion the excipient bears to the ſpecies, or other ingredients, by weighing them after they are made up. For thus you will acquire the greateſt certainty as to their doſes, and will be able to judge whether the common poſologic tables are to be depended on.
Source: wiktionary