"a sleeper bruised and tossing on heaped feather mattresses, the Real Princess"
This refers to the Hans Christian Andersen
fairytale The Princess and the Pea
. It tells of a princess who is made to sleep on a bed of 20 mattresses and featherbeds, with - unbeknown to her - a pea placed under the bottom mattress, to prove to the prince who wants to marry her that she is a real princess. In the morning, on being asked how she slept, she replies that she didn't sleep a wink, as she was tossing and turning all night, and has woken bruised all over. The prince rejoices in her sensitivity, as it proves that she is a real princess, and therefore suitable to be his wife.