Gene, I gave an example(a few posts up) by his response when he came home during a storm and found his terrified wife with her head under the covers, and there are a couple of other explicit "jokes" that I remember in the course of many years of Lincoln studies.
But there is no way I will be repeating them here...on a Sunday no less!
ETA: The description of his humor as decidedly dirty is just my own opinion...others might not feel the same way.