Excerpt from The Book of Priscriptions: With Notes on the Pharmacology and Therapeutics of the More Important Drugs and an Index of Diseases and Remedies In the following prescriptions the quantities according to the imperial system are placed side by side with their practical equivalents according to the metric system. It is not claimed that the equivalents given are exact, but it is believed that the gain in simplicity more than compensates for any slight loss in accuracy of conversion. For instance, an ounce has been rendered throughout as 30 cubic centimetres, or 30 grammes a drachm as 4 cubic centimetres, or 4 grammes a grain as '06 of a gramme a minim as 06 of a cubic centimetre.