Let us take a trip into history and move to 18'th century Anatolia. The province of Erzurum sends agricultural tax (r) worth 1000 pieces of

Let us take a trip into history and move to 18'th century Anatolia. The province of Erzurum sends agricultural tax (öşür) worth 1000 pieces of gold to the Imperial Treasury in Istanbul. Since the distance is considerable and road safety etc is a real concern both the Treasury and the governor of Erzurum prefer alternative payment methods. During a typical year, the animal growers of Erzurum send meat worth about 1000 pieces of gold to the butchers guild in Istanbul. 

Devise a payment method so that the proceeds of the agricultural tax (öşür) is received by the Treasury in Istanbul, WITHOUT actually transporting any gold, from Erzurum to Istanbul.