Casting Out 9s/Historical Note

Historical Note on Casting Out 9s
The technique of Casting Out 9s was probably an invention of the mathematicians of early India.

It appears in 's, dating from about $1150$.

It arrived in Western Europe from the Arabs, via the of $1202$ by.

When initially invented, the technique involved dividing the numbers involved by $9$ and adding the remainders, but the summing of the digital roots has the same effect.