Simplify the following text for a Grade 13 native English-speaking person.
Original: In 1564 , Dee wrote the Hermetic work Monas Hieroglyphica ( `` The Hieroglyphic Monad '' ) , an exhaustive Cabalistic interpretation of a glyph of his own design , meant to express the mystical unity of all creation .
Simplified: In 1564 , Dee wrote the Hermetic work Monas Hieroglyphica ( `` The Hieroglyphic Monad '' ) about a symbol of his own design which stood for the mystical unity of all creation .