What sentence came before this one? (The sentence before is necessary to determine why "neither" is used in this sentence) The sentence basically means, "The secretary never saw Newton drink too much wine, beer, or ale."

= The secretary didn't see Newton take wine, either. There is a preceding sentence which helps to make sense here.

The sentence can be correct - it just depends on what came before it. For example: "The secretary thought Newton was a very healthy man. The secretary never saw him smoke. Neither did the secretary see Newton take wine, ale, or beer in anything but moderation." In this case, the sentence is fine. That's why knowing the sentence that comes before is important - it's the only way to give context for why "neither" is used in this case.

First of all the sentence is not correct. At least it doesn't make sense to me because I have always been tought that: NEITHER can only be used: --> neither = not either of two things or people "We've got two TVs, but neither works properly." "Neither of my parents likes my boyfriend." "Neither one of us is particularly interested in gardening." "Which one would you choose?" "Neither. They're both terrible." "If she doesn't agree to the plan, neither will Tom (= Tom also will not)." "Chris wasn't at the meeting and neither was her assistant." --> informal: "I don't feel like going out this evening." "Me neither." --> neither ... nor = used when you want to say that two or more things are not true "Neither my mother nor my father went to university." "They speak neither French nor German, but a curious mixture of the two." "I neither know nor care what's happened to him." With some corrections the sentence could mean two things: "The secretary saw Newton take neither wine nor ale in anything but moderation." --> the secretaty saw Newton drink a small amount of wine and beer. "Neither did the secretary see Newton take wine, ale or beer in anything but moderation, nor did she (the secretary) see him (Newton) drink any hard liquor." --> the secretary saw Newton drink a small amount of wine, ale or/and beer but not a single drop of hard liquor.