The excerpt below, a parable told by Barlaam the Hermit to King Josaphat, is from William Caxton’s beautiful translation of the Legenda Aurea, The Golden Legend, a collection of hagiographies by Jacobus de Varagine that was widely read in late medieval Europe. Note the black mouse of night and the white mouse of day, gnawing ceaselessly at the Tree of Life. They appear in the illumination (above) and in the carving on the Baptistery at Parma (below). Comparative religion buffs will know that the story of Barlaam and Josaphat is a Christianized version of the story of Siddhartha Gautama, who became the Buddha.
They that desire the delights corporal, and suffer their souls to die for hunger, be like to a man that fled an unicorn that he should not devour him, and in fleeing he fell into a great pit, and as he fell he caught a branch of a tree with his hands and set his feet upon a sliding place, and then saw two mice that one white and that other black, which without ceasing gnawed the root of the tree, and had almost gnawed it asunder. And he saw in the bottom of this pit a horrible dragon casting fire, and had his mouth open and desired to devour him. Upon the sliding place on which his feet stood he saw the heads of four serpents which issued there, and then he lifted up his eyes and saw a little honey that hung in the boughs of the trees, and forgat the peril that he was in and gave him all to the sweetness of that little honey. The unicorn is the figure of death which continually followeth man and desireth to take him. The pit is the world which is full of wickedness. The tree is the life of every man, which by the two mice, that the day and night and the hours thereof, incessantly be wasted and approached to the cutting or gnawing asunder. The place where the four serpents were, is the body ordained by the four elements, by which the jointure of the members is corrupt in bodies disordinate. The horrible dragon is the mouth of hell which desireth to devour all creatures. The sweetness of the honey in the boughs of the tree is the false deceivable delectation of the world, by which man is deceived so that he taketh no heed of the peril that he is in.