I need to find out the origin of the phrase "A penny for you thoughts" Does anyone know?

The earliest recorded use is in a book by John Hyewood, published in 1546, and titled A dialogue conteinying the nomber in effect of all the proverbes in the Englishe tongue. It was a collection of such expressions, so this is not an indication that Heywood coined it, and there not being an earlier record of it is not necessarily evidence that it originated around that time. It may well be a much older expression. The penny referred to at Heywood's time would probably have been worth thousands of times as much as a 2004 American penny.