The four foundations of mindfulness are the body (breathing, changes in posture, activities), feelings (the senses of pleasantness, unpleasantness, and neutrality), the mind (its moods and attitudes), and the objects of mind (which include the five senses but also other mental states and even mindfulness itself.
Waking Up: A Guide to Spirituality Without Religion
It is a 2014 book by Sam Harris. Harris discusses a wide range of topics including secular spirituality, the illusion of the self, psychedelics, and meditation. He attempts to show that a certain form of spirituality is integral to understanding the nature of the mind.