Charles G. Leland 
Fusang [PDF ebook] 
Or, The discovery of America by Chinese Buddhist Priests in the Fifth Century

This book, first published in 1875 and reissued in 1973, analyses the limited evidence from the works of early Chinese historians that explorers from China had discovered a country they called Fusang — possibly western America, and in all probability Mexico. The original document on which Chinese historians based their accounts of Fusang was the report of a Buddhist monk called Hoei-shin, who, in the year 499 AD, returned from a long journey to the east.