Vijnana Bhairava Tantra
वस्त्वन्तरे वेद्यमाने सर्ववस्तुषु शून्यता । तामेव मनसा ध्यात्वा विदितोऽपि प्रशाम्यति ॥ १२२ ॥
When one perceives a particular object, vacuity is established regarding all other objects. (Contemplating on that (vacuity) verily, even though the particular object is still known or perceived, the mind rests in tranquility.
english translation