Well, there's an
introverted flavour to their Intuition. According to Carl Jung, all introverted functions have a "timeless" quality to them because they go under the surface of the everchanging conditions of the external world (e.g. changing societies, culture, fashions, manners, values...) in an attempt to find the eternal and universal natures of things.
So if Si wants to find consistency and permanence in the sensate realm (which is why they like structures and traditions), Ni wants to find the eternals and universals in the intuitive realm. This is why there's often a "mystical", "otherworldly" quality to Ni types. I often imagine Merlin, or Lao Tzu or some other eastern mystic when I think of the extreme Ni type.
In fact, I'd imagine that Ni types were probably a lot more common in the ancient eastern world -- or the ancient world in general -- than they are here in the modern west where the heavily Se and Te culture stifles full expression and development of Ni.