In a discussion about blues music, a friend described the presence of both minor and major thirds in a dominant-seventh tonality as a blues innovation. I wondered if there were examples of dissonant non-chord tones in pre-20th century music that give this effect? The context that popped into my head was an augmented 6th chord (enharmonically equivalent to a dominant seventh) with a leading tone in the melody resolving to the tonic. The leading tone would function as the minor third, against the major third in the augmented 6th. But I couldn't think of any specific examples in pre-20th century music where this actually happens. Can anyone think of such an example?
I think OP's question makes sense; they're asking about a minor third (well, an augmented second) above the bass note of the augmented sixth.
In C, an augmented sixth is A♭, C, and F♯. This is shown below in the "A" example.
But along with the C, I think OP is asking about also including a B, an augmented second ("minor third") above the bass A♭; this is shown above in the "B" example.
Now, regarding the actual question, I can't think of any examples that include both of these scale degrees.
However, while most augmented sixth chords function as pre-dominants, there are augmented sixths chords that function as dominants. One is shown below; note that the asterisked chord includes the augmented sixth from D♭ to B, and the chord is equivalent to a French augmented sixth chord. But note that this chord resolves to a tonic of C, not a dominant in F.
Whether or not this is a bona fide augmented sixth is up for discussion. Often it's just a V43 that then changes to a lowered scale-degree 2 before moving to tonic, but the point here is that this augmented sixth chord does include the leading tone. This is exactly how Bruckner used it in the Adagio of his Seventh Symphony, written in the early 1880s (I start the video at the overall progression, but the chord is at 4:20):