And what, Ananda, is the perception of non-self? Here, having gone to the forest, to the foot of a tree, or to an empty hut, a bhikkhu reflects thus:
The eye is non-self, forms are non-self;
The ear is non-self, sounds are non-self;
The nose is non-self, odors are non-self;
The tongue is non-self, tastes are non-self;
The body is non-self, tactile objects are non-self;
The mind is non-self, mental phenomena are non-self.
Thus he dwells contemplating non-self in these six internal and external bases. This is called the perception of non-self.
Thanks to Jerome Courtemanche for pointing out this passage to me.