Organon 126

The person who is proving the medicine must be pre-eminently trustworthy and conscientious and during the whole time of the experiment avoid all over-exertion of mind and body, all sorts of dissipation and disturbing passions; he should have no urgent business to distract his attention; he must devote himself to careful self-observation and not be disturbed while so engaged; his body must be in what is for him a good state of health, and he must possess a sufficient amount of intelligence to be able to express and describe his sensations in accurate terms.

Organon #126