Medieval salt transport

A man can live without Gold or silver, but not without salt.

Often quoted as being "as expensive weight for weight, as Gold" (a statement I cannot find any confirmation for) it certainly influenced the  creation and  destruction of Empires.
A quick scan of the Internet gave These examples , among many others;
 

In China, Huangdi, the Yellow Emperor, (who  apparently is credited with invented writing, the bow and arrow, the cart, and ceramics),  precided over what is considered as  the first salt war.
 

The city of Rome may have begun as a salt-trading Center.
 

The salt mines of Poland led to a vast kingdom in the 16th century, only to be destroyed when Germans brought in sea salt. The Wieliczka Salt Mine in Poland was started in 1280 and went on producing until 2007!!
 

Venice fought and won a war ( War of Ferrara) with Genoa over salt.
 

The gabelle—a hated French salt tax—was enacted in 1286 and maintained until 1790. Because of the gabelles, common salt was of such a high value that it caused mass population shifts and exodus, attracted invaders and caused wars and was one of the causes of the French Revolution.
 

The Moscow uprising of 1648 is sometimes known as the salt riot, started because of the government's replacement of different taxes with a universal salt tax.
 

Thousands of Napoleon's troops died during the French retreat from Moscow due to inadequate wound healing and lowered resistance to disease - the results of salt deficiency.
 

During the american revolutionary war of 1812, salt brine was used to pay soldiers in the field, as the government was too poor to pay them with Money. and during the ACW, Salt production facilities in Saltville, Va., Virginia's Kanawha Valley and Avery Island, Louisiana, were early targets of the Union Army. The North fought for 36 hours to capture Saltville, Va., where the salt works were considered crucial to the Rebel army - so crucial that Confederate President Jefferson Davis offered to waive military service to anyone willing to tend coastal salt kettles to supply the South's war effort.

 

So, you can see it was important...and highly prized in less industrial times, the cost in the mid 14th Cent was 60 times higher when compared to the period just beforeWWI.
Important because it was used for preservation of foodstuffs and necessary to Keep livestock healthy..an army with sick horses has a huge disadvantage.
Highly prized because it´s production was Manpower intensive, distances from production to end sale/use Long and difficult and therefore costly.

That being the case...any medieval (or come to that pre-motorization) army would have some form of salt supply in the "wagon Train" ..and it would Need guarding.

As far as I can find out, salt was stored and transported in casks (Barrels) .The cask for transport by donkey  was 107 pounds (55 kg)

While salt may or may not have had the same value as Gold it would have been important so it´s Position in the Train would have been central with lots of soldiery (the word soldier Comes from Sal = Salt) around it