One rule that I have for quotations is that if you cannot tell one by heart, it’s better to have it printed on the slide, to avoid problems.
When I usually tell this rule, I have a slide with Abraham Lincoln saying, “You cannot trust every picture with a quote that you find on the Internet.”
I don’t read the text, but people start laughing, and I use this to explain that everything you put on a slide is read by most of the audience. Two rules in one slide 😉
By the way, do you know that most of the quotations that people remember are wrong? This is due to the so-called Mandela Effect.
A famous example of the Mandela Effect is this one: