During the Heian period Nikko-san
 (Mt. Nikko, -san here means mount or mountain),
 Nasu-san (in Tochigi Prefecture)
 and Haguro-san(Yamagata Prefecture)
 were well known as areas where the hard training
 for mountain priests (Yamabushi) took place.
 The mythic being Tengu also lived in these mountains.
 A legend tells that one day Tengu was going from Nikko-san
 to Haguro-san,when he decided to take a rest.
 Sitting against a large rock on Nasu-san he noticed
 hot water coming from under the rock, so he lifted it up
 and threw it aside.
 The hot water rushed out,
 from then on being known as an onsen or spa pool.

 This is the origin of Tengunoyu (Tengu's pool).
 The rock that Tengu is reputed to have thrown is to be seen in the teien (garden)
 by the Oyogiyu(swimming pool),
 so please go and take a look at it!

 Below are some photographs of the rock.

To give you an idea of the rock's size
a person is standing on it!.

This gives you an idea

how strong Tengu is!!

Tengu and reverence for or worship of mountains were basics of the training
for the mountain priests (Yamabushi) living and training in the mountains.
They formed their own grouping completely apart from those governing Japan.
At the beginning of the Tokugawa Shogunate there were about 60,000 people
living in the mountains as Yamabushi.
Tokugawa was alarmed by the large size of this group, not under his power or control.
So Tokugawa Ieyesu took steps to break up this grouping,
he banished or deported the leaders of it and wiped out the rest.
At this time he founded Toshogu shrine in Nikko to counter the worship of Tengu,
destroying the training and worship centers of the Yamabushi at the same time.
The Kurabane-han (region controlled by a daimyo or duke) took control of the Nikko
and Nasu region to destroy Tengu worship and the Yamabushi