Answer
King Mongkut of Siam died on March 1, 1868 while observing a solar eclipse. He had been observing the eclipse with his son, Prince Chulalongkorn, and several other members of the court. As the eclipse progressed, King Mongkut became increasingly agitated and began to speak incoherently. He died shortly thereafter, and his son Chulalongkorn ascended to the throne.