Who invented the at sign?

The at sign, @ - known by more creative names in European foreign languages as the "snail", the "little monkey tail", and the "spider monkey", has many alternative creation theories, including that it developed as an a inside an e, short for "each at", that it was created in the Italian Renaissance by Francesco Lapi, and that it appears in a Norman French painting, as accountancy shorthand, as the word "à".