P46 is the best preserved of three codices containing the oldest substantial portions of the New Testament. You can find out much more at this University of Michigan website.
Originally P46 had 104 leaves containing the letters of Paul. It was written between AD 175 and 225. Eighty-five leaves still exist, thirty of which are at University of Michigan.
The best way I have found to see the P46 pages at the University of Michigan is through a blog that indexed them. The pages at the Chester Beatty Library in Dublin, Ireland, are not available online.