Firstly, I hope this question is within the scope of this exchange.
I know that the character '&' predates its English name "ampersand". I have read that the name 'ampersand' had "entered common English usage by 1837" but the symbol itself is much older, originating as a ligature of the letters "et" which means "and" in Latin.
My question is, how long has the character '&' (not the ligature for et) been used to denote the conjunction word "and"? I cannot find a good source that tells when the shift from the ligature to its own symbol happened.
I found a book written in Latin and published in 1691 that uses the character in this way: http://digitale.bibliothek.uni-halle.de/vd17/content/pageview/7936102
Does this usage of the symbol predate even the 17th century? Do we know of the first recorded use of '&' to represent the conjunction word "and"?