They're only plans and small models, of course.
3 seconds sound clip from the The Sword in the Stone (1963) movie soundboard.
You can hear this line at 00:10:15.974 in the Blu-ray version of the movie.
Quote context
[...]
- He's much too sensitive. Sensitive? Huh? Who? What, what?
- Oh!
- How did you know that I was...
- Oh, that you'd be dropping in? Well, I happen to be a wizard. A soothsayer, a prognosticator.
- They're only plans and small models, of course.
- Now, this for instance is a steam locomotive.
- There she goes. Pretty good, eh?
- That won't be invented for hundreds of years.
- Oh. You mean you can see everything before it happens?
- Ah, ah, ah, ah. Everything, Merlin?
- Uh... No, no, not everything.
[...]