ELEVATION OF SERUM COPPER FOLLOWING COPPER SULFATE AS AN EMETIC
https://pediatrics.aappublications.org/content/42/1/189
Copper sulfate containing 100 mg of copper was administered to 6 children. In all cases, it was successful; they vomited.
“Copper sulfate in a dose equivalent to 100 mg of copper was administered orally to six young children who came to the outpatient department because of ingestion of substances in toxic amounts.”
Perhaps copper was also used because copper is a detoxifier?
Medical Uses of Copper in Antiquity
https://www.copper.org/publications/newsletters/innovations/2000/06/medicine-chest.html
“Until recently, just as in Pliny’s time, the medical profession used copper sulfate as a means to clinically induce vomiting. This is based on the fact that one of the body’s natural physiological responses to prevent copper intoxication is vomiting. A Manual of Pharmacology and its Applications to Therapeutics and Toxicology, published by W. B. Saunders Company in 1957 recommends the use of 0.5 gram (500 mg) of copper sulfate, dissolved in a glass of water, in a single dose, or three doses of 0.25 gram fifteen minutes apart, for this purpose.”
I have read that up to 2.5 grams, or 2500 mg of copper sulfate, was used to induce vomiting by the medical establishment.
This also goes to show that copper is safe, in rather large amounts.
While they claim that the body naturally vomits copper to prevent copper intoxication, this is not the only plausible reason. I believe that the body tends to vomit excess copper because copper rapidly attracts fluoride right into the stomach and that it is the high concentration of fluoride that the body reacts to, by vomiting.