The Priest Mongaku at the Waterall of Nachi by Kuniyoshi Utagawa.

I love this woodblock print despite the story behind it which is rather unsavory.  The picture itself reminds me of O Sensei and his misogi or purification training.  The story goes that a warrior named Endo Morito fell in love with a beautiful woman named Kesa Gozen who was already married to a palace guard named Wataru.  Endo relentlessly pursued Kesa and each time she rebuffed his advances until one day she gave in on the condition that Endo kill her husband the next night.  On the night in question, she cut off her hair and laid in Wataru's bed.  Endo quietly entered the room and killed Wataru and cutoff his head.  He only realized that he had killed Kesa as he ran out of the room with the head.  Upon realizing his mistake, he confessed to her husband and mother and begged them to kill him.  However, Wataru was satisfied with his confession and spared his life.

Being spared and grief stricken with his crime, Endo chose to live in exile and entered into the priesthood and took the name Mongaku.  Interestingly, Wataru entered into the monastery as well with Endo.  Everyday he meditated under the icy falls of Nachi to atone for his crime.  For three years, every day he fulfilled his vow meditate under the falls.  One day during winter, he had almost completely frozen over and was about to die as he meditated.  At the moment right before death, Fudo Myo-o and Kannon, the goddess of compassion came down and saved him.  After his rescue he became an adviser to Shogun Yoritomo and would eventually be exiled to Okishima for plotting against the Emperor.