John Carter, it is not your call, or any other editor, to decide which primary sources are relevant by putting conditions on which sources should be allowed and which should be excluded.  The very act of doing that is analysis and interpretation.  As I already pointed out below, that is a clear violation of WP:OR.  It is up to the reliable secondary and tertiary sources to decide which primary sources are relevant.  Your inability to see this simple point, imho, results from a type of confirmation bias.