 Other Romans who visited Posidonius in Rhodes were Velleius, Cotta, and Lucilius.Ptolemy was impressed by the sophistication of Posidonius's methods, which included correcting for the refraction of light passing through denser air near the horizon.Ptolemy's approval of Posidonius's result, rather than Eratosthenes's earlier and more correct figure, caused it to become the accepted value for the Earth's circumference for the next 1,500 years.