My Dad did just that back in the early 50's, as a brakeman on a work train on the Northern Pacific. There were deep and wet weeds, tight along the Moclips branch where he was working, so, to get from the engine to the caboose, he went across the top. They were spreading cinder ballast, a few cars back, and he jumped from a box, to the top of the cinders, just as they opened the doors! He went through, and was spitting cinders when they pulled him out. He claimed he was picking cinders out of his ears and hair for about 30 years!