Apothecaries' system measure precious metals and stones. (The troy pound was already declared illegal for most other uses by the Weights and Measures Act of 1878.) In the US, the metric system replaced the apothecaries' system in the United States Pharmacopoeia of 1971. Apothecaries' system The apothecaries' system or apothecaries' weights and measures is a historical system of mass and volume units that were used by physicians and apothecaries for medical recipes, and also sometimes by scientists. The English version of the system is closely related to the English troy system of weights, the pound and grain being exactly the same in
Yarn weight Yarn weight Yarn weight refers to the thickness of yarn used by knitters, weavers, crocheters and other fiber artists. Changing yarn weight or needle size can have a significant impact on the finished project, so standardized systems have been spread about, as well as conversion systems for regional standards (especially needle sizes). Yarn weight is important in achieving the correct gauge or tension for a particular project and can help with yarn substitution. The Craft Yarn Council of America has developed a system that seeks to standardize the labeled weights of yarn. Most yarns state their weight on the ball