Evidence that this has been taken literally:
Long ending of Mark (spurious to Mark yet "canonical" to almost all Christian confessions):
And these signs will accompany those who believe: by using my name they will cast out demons; they will speak in new tongues; they will pick up snakes in their hands, and if they drink any deadly thing, it will not hurt them; they will lay their hands on the sick, and they will recover."
The Maltese episod in Acts 28:
Paul had gathered a bundle of brushwood and was putting it on the fire, when a viper, driven out by the heat, fastened itself on his hand. When the natives saw the creature hanging from his hand, they said to one another, "This man must be a murderer; though he has escaped from the sea, justice has not allowed him to live." He, however, shook off the creature into the fire and suffered no harm. They were expecting him to swell up or drop dead, but after they had waited a long time and saw that nothing unusual had happened to him, they changed their minds and began to say that he was a god.