Ted Ehara wrote:
Misogi is spiritual purification. Shinto doesn't believe in sin, but does believe that you can pick-up spiritual impurities though daily living. When you get dirty, you can take a bath. When you pick-up spiritual grime, you can perform misogi. Therefore it becomes important to purify yourself spiritually on a frequent basis.
Misogi is not only done through water. You can do misogi though other ways like bell ringing and chanting. So water misogi is not the only form of purification. This brings us to the founder's statement, "Aikido is misogi."
I think he is actually trying to express the idea that the practice of aikido is a form of spiritual purification. This viewpoint reflects his shinto background and understanding of aikido as a spiritual practice.
When he says, "Aikido is misogi", he means the practice of aikido is an act of spiritual purification. Hopefully he is right and we are all better people for it.
Kevin, Ted put it well above. Misogi with water, when icy cold, strengthens the nerves, the tanden, concentration, and the constitution.
But as Ted so well described, Misogi can be a multitude of practices.
Nakazono said Misogi is washing out. Or cleansing.
Your 100 Km hike sounds like a Misogi type practice, with silence.
How can you not get even a little bit in tune with God through nature after 5 days of that.
Coming back to civilization after that must be a little shock.
So, any action/thought/practice which builds you body/mind/spirit
and purifies your being is Misogi and builds good karma. They are all very general terms, to me.