Can the perceiver be perceived? Can the seer be seen?
The perceiver is the Self. Meaning it is You (I) that perceives, whatever that You (I) is. You (I) perceive perceptions, thoughts, sensations. Those are phenomenal events that appear to You (I).
But that (I) which perceives is not phenomenal and thus cannot be perceived as you perceive an oak tree or a passing cloud.
Although you do not perceive yourself as you perceive the surface of a pond, it is undeniable that you know you are.
You know you are aware and that you are aware of being aware. The I AM is undeniable. Probably overlooked, but undeniable.
This self knowingness is undeniable. You know yourself since you are yourself, you are the Self that knows itSelf. This knowingness is non phenomenal and is undeniable.
Whenever you look for yourself, there you are. Yet, whenever you look for the oak tree, you may or may not find it.
In short, you do not perceive the perceiver phenomenally. You ‘apperceive’ (non phenomenal knowingness) the perceiver since you are that.
That which does not come and go, which you know as yourself is the non phenomenal non dual Self.
It is both the knower and the known, without any separation.