In the "pactum Lotharii" of 840 between Venice and the Carolingian Empire, Venice promised not to buy Christian slaves in the Empire, and not to sell Christian slaves to Muslims. The Venetians subsequentently began to sell Slavs and other Eastern European non-Christian slaves in greater numbers. Caravans of slaves traveled from Eastern Europe, through Alpine passes in Austria, to reach Venice. Surviving records valued female slaves at a "tremissa" (about 1.5 grams of gold or roughly of a dinar) and male slaves, who were more numerous, at a "saiga" (which is much less). Eunuchs were especially valuable, and "castration houses" arose in Venice, as well as other prominent slave markets, to meet this demand.