From a 1973 interview with Rick: “Yeah, the thing in the last panel was a Greek epigram. It reads the same if you read it across or up and down. That was a literal translation that was written in the small panel across the bottom. It was all in a effort to know my creator. I’ve since gotten to know him through his son Jesus Christ. I changed that to leave reference that it was an epigram and the other contents were pre-salvage mumbo jumbo..”
Some say a better translation is: “The sower, with his plough, holds the wheels with care.”
The 2020 Christopher Nolan move Tenet — which was the last movie I saw on a plane and was kind of amusingly incomprehensible — has references to this epigram all over it FWIW.