Surprisingly the author actually did his research on cholera. The cause of death from cholera is normally a combination of dehydration and electrolyte imbalance (usually hypokalemia and sometimes hypophosphatemia), both of which can be treated with a simple oral rehydration solution that contains salt, potassium, and phosphates. Ephedra contains the vasopressors ephedrine and pseudoephedrine, ginger contains potassium, almonds contain phosphates, and lavender is a flavoring agent(?). Unfortunately for this to work in real life, this makeshift oral rehydration solution would need to be administered repeatedly over the course of several days to replace lost fluids and electrolytes. Ephedra also has a variable amount of ephedrine and pseudoephedrine, and these drugs carry a significant risk of fatal overdose. The biggest unrealistic aspect of the treatment is the boy springing up as though nothing is wrong afterward, as he would still be very sick for several days fighting off the infection.