eṣa ma ātmāntarhṛdaye’ṇīyānvrīhervā yavādvā sarṣapādvā śyāmākādvā śyāmākataṇḍulādvaiṣa ma ātmāntarhṛdaye jyāyānpṛthivyā jyāyānantarikṣājjyāyāndivo jyāyānebhyo lokebhyaḥ || 3.14.3 ||
3. My Self within my heart is smaller than a grain of rice, smaller than a grain of barley, smaller than a mustard seed, smaller than a grain of millet, smaller even than the kernel of a grain of millet. The Self in my heart is larger than the earth, larger than the mid-region, larger than heaven, and larger even than all these worlds. Chāndogya Upaniṣad, 3.14.3
Sorry to interrupt Upāsika Ceisiwr’s question, venerable! But just because I actually already wrote about this, I thought I would link you to three previous comments of mine. I argued that the findings of physics and so on are not generally in the same category as Buddhist emptiness, and it is a separate field of investigation than what the Buddha was discussing. But at the same time I also said that we do need to know that everything is insubstantial, including grains of sand. I don’t see them as incompatible. I think you would agree.
