Illusion must appear. It is hard to imagine a non-appearing illusion. There must be something capable of deceiving us; causing us to believe in the false. In this regard, negation has to be seen as the cancellation of the illusion, i.e., the false. We can get a sense of this when Nagarjuna says, "The ambrosial teaching of emptiness aims at abolishing all conceptions (sarva-saṁkalpana)." Certainly conceptions count as illusions in the sense of being representations—mind formed images.
We can also think of the illusion as conditioned or the same, composed reality. Our psychophysical body is such a composition as is the world outside of it which is always confronting and deceiving us. When the Pali Nikayas speak of the purified and incomparably highest emptiness, that is, parinibbutā parisuddhaṃ paramānuttaraṃsuññataṃ it is the total cancellation of conditioned or composed reality. What remains is nirvana the unconditioned reality, the supreme end.
Emptiness, while being the cancellation of the conditioned which is illusory, cannot empty out the unconditioned (the absolute). It can only empty out that which is conditioned and adventitious. For example, we can empty out the cookie jar of its contents but the jar remains. To say the cookie jar is empty means it is empty of cookies. The notion or idea of an invisible "empty jar" is heading in the wrong direction. On this track, we can by meditation bring about the cessation (nirodhaḥ) of mind conditions or as Patañjali in his Yoga Sutras called them, citta-vṛtti, that is, mind modifications. At once the mind conditions or modifications are cancelled out. With this instantaneous cancellation there before us is the unconditioned, the eternal, true emptiness. Every part of us including our temporal thought is engulfed in a hard to describe, mysterious luminosity which transcends conditionality. It is not that there is nothing there, there is. It is just not conditioned.