Curare was used by the Indians as a poison on their arrows.

It caused paralysis of the person hit by it.

This led to physiological studies in the 19th century. It was later used in surgeries to stop patients from moving (and its derivatives are still used for that purpose today).

physiostigmine is a natural substance produced by the calabar bean.

It was coincidentally found to reverse the effect of curare in anasthesized dogs. http://www.nickalls.org/****/papers/...urare1985a.pdf

Marry walker noticed that patients with myasthenia have symptoms resembling curare poisoning. That is why she tried physiostigmine.
But, this natural substance had significant side-effects.

The pharmaceutical company Roche developed a synthetic substance which was more tolerable-prostigmine. (later the name was changed to neostigmine and is still used by anasthesiologists to reverese muscle relaxation after surgery)

This was given to another MG patient with better results.

http://www.ncbi.nlm.nih.gov/pmc/arti...0680-0107b.pdf

Pyridostigmine was developed later as an oral medication. As was oral prostigmine and mytelase.