https://books.google.com/books?id=GNxkBwAAQBAJ&pg=PT68&lpg=PT68&dq=spanish+explorers+dead+reckoning&source=bl&ots=da4izkzk6w&sig=B6-nEmzBlcxrqpkhxJuMwJ7ablM&hl=en&sa=X&ved=0ahUKEwiT7LWbpZLWAhXFylQKHXFoCbsQ6AEIQDAI#v=onepage&q=spanish%20explorers%20dead%20reckoning&f=false
The Florida of the Inca: A History of the Adelantado, Hernando de Soto, Governor and Captain General of the Kingdom of Florida, and of Other Heroic Spanish and Indian Cavaliers
By Garcilaso de la Vega, John Grier Varner, Jeannette Johnson Varner
https://www.questia.com/library/66001330/the-florida-of-the-inca-a-history-of-the-adelantado