Know a Mentat by his red-stained lips.
5 seconds sound clip from the Dune (1984) movie soundboard.
You can hear this line at 00:19:47 in the Blu-ray version of the movie.
Quote context
[...]
- Because of her love for the Duke, she disobeyed and gave birth to a son, Paul. Paul Atreides.
- The training planet of the Mentats, the human computers.
- Know a Mentat by his red-stained lips.
- Carryalls lower the harvester to the sand, and lift it off to safety when a worm attacks.
- Worms attack all rhythmic vibrations.
[...]