Answer:
A medieval illustration that was painted in 1211t, that depicts a peasant man harvesting wheat, would be extremely valuable to a historian, because they would have almost a first hand perspective of how farming was done back in those times and what tools they used to do so. Not to mention the fact that someone then, painted a picture of something that might seem random like farming to us now, can potentially tell a lot about the painter and their motives, and what people considered to be art back then. For all we know, the painter could have been trying to illustrate what work was like for a peasant.