I don't think McGonagall ever wrote about bosoms, Amos. He would have become overwrought, I imagine, trying to deal with such a sensitive subject. He did, however, write reams of passionate verse regarding the evils of drink. It would be most un-McGonagallesque to write about bosoms, except in a phrase such as "the bosom of his family and country". They used to even cover the lower limbs of furniture in those times, don't forget, as it might be too suggestive to expose them to the public gaze.

Still, they did manage somehow to propagate further generations...so I suspect some bosoms must have been seen here and there under certain circumstances.