I have been doing a bit of research on camelback locomotives as used by most of the anthracite railroads in Pennsylvania and New Jersey. The cabs on these engines were quite narrow since they were straddling the boiler, and often the firebox behind the cab was wider than the cab. For this reason, as well as trying to stay cool, the engineer often sat on the cab window sill, in much the same way that engineers on some of the Maine two-footers also sat on the window armrest.
My research came across the the term "on the cab," which apparently commonly used to describe this practice on the wide gauge railroads. Have any of you folks heard this term in connection with the narrow gauge?