Pliny

Naturalis Historia 2.236 (c.79 AD)

The Chimaera, rationalised.

nec in illo tantum natura saevit exustionem terris denuntians: flagrat in Phaselitis mons Chimaera, et quidem inmortali diebus ac noctibus flamma.

DSS no. 52. Translation can be found here.