16th & 17th C
Thirds were usually played with fingers 2 & 4, sometimes with 1 & 3.
Fast parallel thirds were always played with fingers 2 & 4 (Couperin + C.P.E. Bach)
Sixths were mostly played with fingers 1 & 5, with 2 & 5 used when the lower note is an upper key.
Many sixth chords were often played with 2, 3 and 5 as this avoids excess inwards turning of the thumb.
18th C
Thirds, in slow movements, were played with 1 & 3, 2 & 4, and 3 & 5.
It is still recommended that 2 & 4 are used in faster passages.
Sixths - as above
19th C
Thirds - parallel thirds were played with 3 & 1 and 4 & 2. Occasional exceptions occur when upper keys are involved.
Sixths - parallel sixths were played with 4 & 1 and 5 & 2. Again, this was fairly consistent, but exceptions occur again where upper keys are involved.