IIRC Pliny the Younger gave a first–hand account of Pompeii and his uncle (the Elder) during the eruption. Some of Josephus’ writings were failry contemporary, although the passage on Jesus is alleged to have been embellished. If instead of original text you mean original manuscripts, not copied… good luck with that.
That was somewhat hyperbolic there are some ancient events we have multiple independent first hand accounts of. Though of course unbiased sources do not exist, whether we are talking a polemic by a 1st century Roman aristocrat or a impeccably researched 21st century history
That gives me a chance to bring up my current favorite podcast the constant. I just heard their episode on…
Who believed all historical writings (and all the events to they described) prior to 14th century to be made up
One random fact I discovered googling the OP is it was his invention that Caligula was specifically declaring war on Neptune, with his beach side military excursion, rather than declaring war on the sea.