Fingering
Ideas about fingering have changed during the history of music.  In the Baroque times (17th and early 18th centuries) French composers writing for the harpsichord often fingered scale passages 2 3 2 3 etc. so that the notes were grouped (slurred) in twos.  Later this idea went out of fashion.  In the early 19th century  Carl Czerny wrote lots of studies for piano  which helped to exercise all the fingers equally.  This is how we learn to play the piano today.