Christian Heinrich Heineken (February 6, 1721 – June 27, 1725), also known as “the infant scholar of Lübeck”, was a legendary German child prodigy. When he was eight weeks old, he could speak German. He read the Pentateuch at age one, and between the ages of two and three, he read the Old and New Testament in Latin. When he was three years old, he was said to have authored A History of Denmark and recited it when visiting the King of Denmark later the same year. He died at age four of celiac disease.
While his exploits certainly seem hard to believe from a current perspective, they are relatively well documented for the standards of the time, e.g. Immanuel Kant wrote an essay about the child (calling him an “ingenium praecox”.) He was breastfed until close to this death, which was very likely caused by the ingestion of grain products.