[…] a rural citizen entered a druggist's shop and asked for ten cents' worth of magnesia. The drugger gave him some of Husband's magnesia, and labeled it as such. In half an hour the purchaser returned, and said he wanted ten cents' worth more. The drugger told him that he had given him a full dose. "I know that," replied the man; "I want this for my Wife!"
Source: wiktionary