For when the first time the Senate chose the emperor, they chose Nerva in 96 A.D., which was a wise choice. Nerva equally chose four successors, which were Trajan, Hadrian, Marcus Aurelius, and Antoninus. Nerva made sure that he had the support of the military by adopting his son and joint ruler commander of Upper Germany, Marcus Ulpius Trajanus. Nerva also swore to never execute a Senate member. http://www.the-romans.co.uk/good_emperors.htm