In his famous “Dharma Lesson in Japanese” or tetsugen zenji kana hōgo (鉄眼禅師仮名法語), the Japanese Zen-Buddhist monk Tetsugen (mentioned here in earlier post), wrote in the fourth section:
When you see images reflected in a bright mirror all day long, it reflects the sky, the land, flowers, willow trees, people, animals and birds. All the colors change and the types of things [reflected] change without a moment’s rest, but the true form of the mirror is not the birds and animals, or the people, or the willows, flowers, the land, or the sky. It is just the shining and unclouded mirror itself. Our original minds reflect and illuminate the ten thousand dharmas, but have no connection to their distinctions.Translation by Helen J Baroni, from Iron Eyes: The Life And Teachings of Obaku Zen Master Tetsugen Doko
This is based on earlier Yogacara-Buddhist teachings, and can be pretty hard to grasp beyond a surface-level intellectual standpoint. It takes considerable time, practice and introspection to finally “get it”.
Dr. Helen J. Baroni, comments elsewhere in the book:
The mind, like the mirror, is independent of the images it reflects and remains unchanged by them. Therefore, there is no need to purify it of them. While it is possible to quiet the flow of psychic constructions in meditation, there remains a dualism inherent in the practice. For the enlightened mind, the mirror should be visible “even if images of blossoms and willows are reflected.”
Pretty deep stuff.