Complex sentence: He proposed a potentially deadly experiment to be done during an electrical storm where a person was to stand on an insulated stool inside a sentry box, and hold out a long pointed iron rod to attract a lightning bolt.
Split into simpler sentences: He proposed an experiment to be done during an electrical storm where a person was to stand atop an insulating stool inside a sentry box. He was to hold out a long pointed iron rod to attract a lightning bolt.