travel... on the sea

Do you know, how many times took a merchant boat from  Alessandria of Egypt to Amalfi ?

 

We have an answer, thanks to a letter wrote by a jewish merchant during the XI century, discovered in Al-Cairo.

That letter give us many information about the Amalphitain ship course from Alessandria of Egypt, throught the Messina channel, to Amalfi.

But that travel, instead of  last 15 days, it lasted 75 days, because  there was a pirate squadron followed them and they frequently changed rigging.