Jules Levy was one of the finest cornetists to ever play our instrument. He was a recording pioneer, and the music he left behind for us set the bar for trumpet performance for the next century. He left behind two methods, one is his instructional cornet method, which will be available soon, and the second is this set of 6 studies. It is a short volume, but it is a fantastic record of the dexterity, flexibility, and technical aptitude Levy expected from trumpet players. The ability to perform these 6 studies would be a feather in the cap of any trumpeter.
You can see the first page in the samples, and you can grab a PDF download above.