caffeine is about thirty times more toxic than glyphosate. According to wikipedia:

"The LD50 of caffeine in humans is dependent on individual sensitivity, but is estimated to be 150 to 200 milligrams per kilogram of body mass (75–100 cups of coffee for a 70 kilogram adult)"

For glyphosate: "The acute oral LD50 in the rat is 5,600 mg/kg. Other oral LD50 values for glyphosate are 1,538 to greater than 10,000 mg/kg for mice, rabbits mg/kg, and goats"

http://pmep.cce.cornell.edu/profiles/extoxnet/dienochlor-gly...