In the book "Ancient Mines in Bulgaria" by Veselin Bozhikov, published by Sfera Publishing House in 2008, there is a text concerning an ancient Roman mine in the land between the villages of Kalotina and Berende izvor:
You will go to the ground between the village of Kalotina and Berende izvor. There is a place called Refugee. There, on one stone, three yards wide and two high, we forged pig targets and 7 piglets. From the target on the west side there is a dry valley. Go across and you will come out on a long meadow. There are three drill holes made in a meadow of an arshin stone. From this target, 4 steps on the east side of a yard deep under a slab with two gutters, there is a cauldron of Hungarian gold coins.
From there up is the place called the Bad Pass, and from there up is the place Zmiyarnika. In this place in the valley of a stone two yards wide there are forged targets, a hen and 6 chickens. From the stone 12 steps on the east side of the arshin, deep in a clay vessel, there are 35 ounces of gold money.
From there up is the place called the Cave. There, on a stone, is a forged dog's head. A narrow passage will open deep from a target 8 steps to the east of a yard. Here is an old Roman mine.
Since when is the text about ancient mines in Bulgaria dated:
Judging by the other texts in the book "Ancient Mines in Bulgaria", the story in the manuscript is dated to the beginning of the 19th century (until 1850 at the latest).