Is the Correct Pronunciation a U or O?

People will have written out mistakes in texts. They usually crept in because words are pronounced in a certain way, but should be written in a differnt one. The most famous incident of this is the letter, or the letters, what we call dip thong, two vowels being pronounced together,. as in the name of the emperor claudius which the correct pronunciation was claudius acat a u is o. In particular, i'm sure it's hilerius in the original latin, is lost everything in translation.