When the board of county commissioners considers that the public good so requires, it shall authorize and require the county engineer to ascertain, by actual survey and evidence, the corners of each or any of the originally surveyed townships in such county, and there place, perpendicularly in the ground, a stone post, not less than ten inches in diameter nor less than three feet long. The board shall furnish the posts, and all expenses of the county shall be paid from the county treasury.