Bleeding a patient to cure mental illness began around the time of the ancient Egyptians (because art therapy can’t cure everything), and then was taken up by the Greeks, Romans, Arabs, Asians, and eventually Europe, reaching its peak usage around the 19th century. The Greek rationale was that in order to keep the four humors in balance, getting rid of “bad blood” would restore someone to health, and other cultures followed suit with this line of thinking.
The median cubital vein (the one at the elbow where IVs are often placed now) was often used for bleeding, and cuts were made with lancets (small, pointed knives that could be carried in a doctor’s pocket) or a fleam (a device much like a Swiss army knife, with multiple-sized blades that could be folded up).
Leeches were also used, though their placement depended on the area where the physician determined the cause of the illness to be.
We have discovered in modern times that while leeches can be used effectively in some skin and musculoskeletal disorders, using them for mental illness to balance the “four humors” has no merit. Likewise, bloodletting seems to have no practical application today, which goes to show that the people of yore lost a good deal of blood and gained back none of their sanity.