The pilot's visual references when performing the maneuver.

Bottom line

The pilot should become familiar with the relationship between outside visual references to the natural horizon and the corresponding flight instrument indications. Integrated flight instruction is flight instruction during which learners are taught to perform flight maneuvers both by outside visual references and by reference to flight instruments. No distinction in the pilot’s operation of the flight controls is permitted, regardless of whether outside references or instrument indications are used for the performance of the maneuver.