Say that you have a time machine. But in order to prevent paradoxes, the only way you can interact with the past is by mentally communicating with people in their final moments, who can't pass on anything you tell them.
Pick a historical figure to talk to. What do you ask them, and what do you tell them? How do you expect them to react? Do you pick a great person and tell them what they accomplished? A villain to torment with their ultimate failure? Or just a normal person in the hurly-burly of normal life?
This line of thought brought to you by musings of how Henry VIII would have reacted, had he known that his child would solidify so much of what he set out to do -- but that it would be Anne Boleyn's daughter, not Jane Seymour's son, who did it. (I just finished a fascinating course on Henry's life and times. Now I really need to listen to the one that puts it in the context of what happened next...)