Machiavelli places his most famous work, The Prince, well in the tradition of other humanist works which were very popular during the Renaissance. Humanism draws heavily on using examples of actual people to showcase the potential and worth of individuals. In order to show what the quintessential ruler is capable of, Machiavelli had to show his readers what others had done before as both positive and negative examples. This separates his work from the previous medieval period's writings, which focused almost exclusively on biblical and saintly characters as models for how humans should behave.
Some examples that Machiavelli includes to illustrate his political theory harken back to the Classical period of Greece and Rome. Since the Renaissance was a resurgence of Classical thought, this was a natural direction for him to take. In Chapter XIX, Machiavelli describes the reigns of many Roman emperors. Emperor Marcus Aurelius, Pertinax, and Alexander are shown as examples of rulers who lived modest and philosophical lives. These were benevolent rulers who were loved by their people. However, this did not mean that they were immune from treachery. Machiavelli tells of how Pertinax was overthrown by his soldiers because he did not dote on them the way his predecessor, Commodus, did. Machiavelli describes this as a case in point that "hatred is acquired as much by good works as by bad ones."
He also provides examples of cruel Roman Emperors such as Commodus, Severus, Antoninus Caracalla, and Maximinus. These were cruel and unprincipled rulers. Machiavelli uses them as examples of what happens to rulers who favor their soldiers over their common citizens.
When reading The Prince, you will find that is full of historical examples of rulers. By doing so, Machiavelli is showing his readers that his work is more than just a treatise on an idea—rather, he relates a thoughtful historiography that examines real-life examples through the lens of Renaissance thought.