Where did the @ Symbol come from?

We use it everyday but have you thought of where it came from? Turns out that it has several possible origins from a medieval Monk shorthand in Latin transcriptions to French penmanship to Florentine merchants setting pricing per unit measurement. 

However it was  Ray Tomlinson in 1971 that made it into the frequently used symbol we think of today denoting which server your email address resides (not to mention the Twitter handles of today).