That the world and everything in it is unreal is a theme of the Upanishads. Here are a few extracts from the third chapter of the Tejo-bindu Upanishad
‘The form of the mind is false. The form of the intellect is false. I am eternal, perpetual and originless…the three bodies are false, the three gunas are false, all scriptures are false, the Vedas are false, all Shastras are false, I the Atman of consciousness am true. The triad of murtis are false, all beings are false, all truth is false. I am Sadashiva, pervading all existing things. The preceptor and pupil are false, the mantra of the preceptor is false.. Whatever is seen is false, what is conceivable is false… all living creatures are false, all enjoyments are false, right and wrong action is false, what is lost and obtained is false, grief and delight are false, good and bad conduct is false. All form, taste, smell, cognition is false, every result of human existence is false, I alone am the absolute Truth.
A passage follows on the mantra ‘I am Brahman’ which supersedes all others and destroys all duality, all diseases of the mind and all bonds. This mantra alone should be used.