Hari Sauri: During his midday massage, Prabhupada suddenly started talking about dreams. He told me that last night he dreamt the temple courtyard was completely flooded. He said he was thinking, "Oh, if it comes even one more inch, everything will be spoiled."
Thinking there might be some significance to his dream, I asked him what dreams were. Prabhupada replied in a general way, saying that they are impressions stored within the mind, not just from this lifetime, but also from previous ones. The dream is illusory but the objects are real.
Chuckling, he pointed to the plastic bottle of mustard oil I was using. "Here is a bottle of oil, and here is the bed. Both are real, but if I take the oil and put it under the pillow then it has no meaning. The pillow and oil are real, but I am crazy. That example is there in the Bhagavatam, of gold and a mountain. I have experience that there is gold, and there is mountain. I have no experience of a golden mountain, but in dream they combine."
Reference:A Transcendental Diary Volume 4 - Hari Sauri Dasa