From Lost Japan by Alex Kerr.
Japan is fascinated by secrets. They are the defining feature of the way traditional arts are taught and preserved. They cause problems for governments and business, since different departments of the same organization tend to guard their knowledge jealousy and not speak to one another. In museums, the finer an artwork, the less it will be shown to the public - which is why you will often find that the National Treasure you travelled so far to view is actually just a copy. The real piece stays in storage, and is shown only to a chosen few curators.
This tradition goes back to ancient Shinto, when the objects inside shrines, typically a stone or a mirror, became invested with mystical secrecy. At Izumo, Japan’s oldest Shinto shrine, the object has been hidden from view for so long that its identity has been forgotten; it is referred to merely as "the Object." At the Grand Shrine of Ise, the object is known to be a mirror, but no one has laid eyes on it for at least a thousand years. When asked about Ise, the nineteenth-century Japanologist Chamberlain replied, "There is nothing to see, and they won’t let you see it."
Buddha statues with great power became hibutsu (hidden Buddhas), and were displayed only once every few decades, and there are some that have stayed in hiding for centuries at a stretch.
That evening, we stayed at Kongo Sanmai-in, one of the sub-temples that offer rooms to pilgrims and travellers. We arrived at our lodgings at around half past four. One of the monks asked us if we would like to see the Buddha in the main hall, but we were all exhausted. After an early supper, I went to my room to read a book and relax for a while. That night, on my way to the bath, I passed a monk in the hall. "Good evening," he said pleasantly. "How fortunate for you to have come here today. You were able to see our great Buddha of divine power."
"Well, actually we were planning to see it tomorrow," I said. The monk shook his head. "I’m afraid that won’t be possible. Sanmai-in’s Buddha is a hibutsu. Mt. Koya’s other statues are sometimes put on display, or even lent to other temples and museums. But this one has never left the mountain. This is the first time it has ever been shown to the general public. It’s called a five-hundred-year hibutsu. the doors closed at five o’clock today, and you’ll have to wait another five hundred years if you want to see it."
This was my greatest failure ever as a travel guide. I was so embarrassed that I could not bring myself to confess to my friends, and to this day I don’t believe they realize that they missed seeing a five-hundred year hibutsu by only thirty minutes.