So, logically... If she weighs the same as a duck... She's made of wood.

— Sir Bedevere (Terry Jones)

13 seconds sound clip from the Monty Python and the Holy Grail movie soundboard.

You can hear this line at 00:19:52 in the Blu-ray version of the movie.

Quote context

[...]

- Mud.

- Churches.

- Lead.

- A duck!

- Exactly.

- So, logically... If she weighs the same as a duck... She's made of wood.

- And, therefore...

- A witch! A witch!

- We shall use my largest scales.

- Right. Remove the supports!

[...]