I purchased this exact trivet below at a craft fair, back in the 60's, and it has been in daily use since that time, which gives a lot of credit as to its durability. However I never cared for the center the large center space and the center hole.
I believe at one time there was a written version of the original trivet in Crochet World Magazine, but I have so many books and it has been so many years, I doubt I would chance to find it now. So I cannot provide a source for the pattern of this old trivet.
Over the years I have tweaked and modified the structure of the pattern and it changed / developed. So what you will find here is my reworked version of the pattern.
There are other similar patterns on the internet, however I like my pattern better. It takes less yarn and fewer rows, but still provides an impressive trivet.
I make several variations of this pattern all are posted on this blog.
An excellent tutorial for the Popcorn stitch can be found here