Christian Saints

        St. Sergiy Radonezhskiy (about 1321-91) religious and political figure of the 14th century, founder of the Troitse-Sergievsky monastery, before taking monastery vows he was called Bartholomew. He was spiritual instructor of the Prince Dmitry Donskoy, and enthusiastic supporter of the Prince’s policy against Tatar-Mongolian occupation. The legend about his youth says that the Bartholomew, a pious boy, could not learn reading and writing, though he wished it with all his heart. He prayed for being helped. Once, looking after cattle, he met a divine hermit, and asked him to help him in learning. His plead was heard. Sergiy Radonezhsky was canonized by the Russian Orthodox Church.
See: Mikhail Nesterov Youth of Saint Sergiy Radonezhsky, Vision to Youth Bartholomew.
Victor Vasnetsov St. Sergiy Radonezhskiy.

Recommended reading:
The Wonderful Life of Saint Sergius of Radonezh by Alvin Alexsi Currier, Nadezda Glazunova (Illustrator). Conciliar Press, 2001.
Saint Sergius and Russian Spirituality by Pierre Kovalevsky, W. Elias Jones (Translator). St Vladimirs Seminary Pr, 2001.