Tylenol #3's contain the following active ingredients: As for the recreational use of T3's, I recommend against taking more than the recommended dosage - which is 4 within a 12 hour period.
LD50 for codeine is apparently 800mg (though I wouldn't exceed 500), so you're not likely to overdose on the opioids, but rather, the tylenol.

It's worth noting, though, that acetaminophen is not water soluble at room temperature... Codeine is.

If you wish to safely enjoy misusing prescription drugs, I recommend you add the crushed pills to room temp. water and pass through a coffee filter. The acetaminophen will be filtered out - leaving you with a bitter solution of codeine and caffeine you can then drink without fear of tylenol overdose.