i *finally* found that chart i'd recalled seeing but couldn't recall where. it was part of this Whole Health Source post. here's the chart and some accompanying verbiage:
The ideal ratio is probably very roughly 2:1 omega-6:omega-3. Leaf lard is 6.8, beef tallow is 2.4, good quality butter is 1.4, corn oil is 45, cottonseed oil is 260. It's clear that a large qualitative change in our fat consumption occurred over the course of the 20th century.