<VV> recipe for mouse poison, please!

[Wrsssatty at aol.com]

First, let me apologize because I know this has been discussed ad nauseam  
here before but I didn't need the info until now....
 
Could someone please share with me the recipe for mouse poison?  I  think 
it involves flour and concrete mix.  
 
A private reply is fine.
 
And, is there any way to be sure a mouse nest isn't blocking your airflow  
without removing the shrouds?
 
Thanks!
 
~Bill Stanley