Yes that is true, but if you don’t have a permanent written record of the computation, that takes away a lot of the advantage of written arithmetic. You may as well just use your counting board.
Not permanent, but a record that could be shown as the computation was performed, and until the slate itself was erased. Obviously, where a permanent record is desired, permenent media would be used.
My point was that there were cheap alternatives to parchment and paper for quick work.
A wax or clay tablet or flat patch of dirt and a stick, piece of bark or wood and charcoal, etc. don’t have enough advantage for anyone to bother organizing their accounting or calculation system around them. They are on the whole inferior to the existing system. Trying to introduce them to people 2000+ years ago might have a chance, but it would be a tough sell.
The thing that really spread Hindu numbers around the world was access to paper.
My impression is that in India “Hindu” numerals and arithmetic were developed using some kind of erasable board, but among Arabic speakers (and later Europeans) the spread of Hindu numerals went along with paper as a prerequisite technology.
It's probably worth noting that Fra Luca Bartolomeo de Pacioli's dates are c. 1447 – 19 June 1517, shortly after Gutenberg and about 50--100 years after cheap papermaking (comparatively) first reached Europe.
It's hard to have double-entry bookkeeping without books.
I'm unsure if he used Arabic or Roman notation... Though the dedication page of Summa Mathematica in fact does include recognisable Hindu / Arabic numerals:
Wikipedia's article has several illustrations, but none of the actual bookkeeping notation itself, which is ... a curious oversight. Continued on the double-entry bookkeeping article as well FWIW.
