Mentat

In the novel “Dune” Frank Herbert described a post-computer world where “mentats” performed rapid and complex calculations for the noble houses of humanity.
These specialists were not just raw computational experts, but they were valued for their ability to sift through mountains of data to provide vital analysis.
When noble houses warred, assassinating the enemy’s mentat was a priority.
That is why the messenger was killed and searched thoroughly. Then analyzed for poison.
“It’s safe,” I say. “Just plain paper.”
I hand the mentat the message, and he has a stroke and dies!
What? How?
“Divide by zero,” it says.