You'll note that the first part of the quote is missing, and I'm looking for it, but I'm not sure I'll find it, but not to say it doesn't exist.
A large number of useless books utilize this quote, and I mean the first part of the quote in particular, and refer to secondary sources as their source, which themselves use secondary sources. It's absurd how modern scholarship prizes itself on listing one's sources, and I have to wade through a lot of nonsense.