Natural hygrometers
Plants often react to humidity. But the changes they exhibit due to presence of moisture are not always noticeable. However pinecones react explicitly to humidity. When the moisture level is high the cones close their spines tightly. But when the moisture is quite low the spines of the cone opens up. Although thy will not give an accurate data about the level of humidity, they will give you an overall idea.
Arty hygrometers
These were commonly seen in homes. These are in shape of wooden boxes in which a little woman and a little man stand in two different door ways. When it is cloudy and going to rain, the man comes out with an umbrella and when it is dry the woman is out. The mechanism that works inside the weather house is that the figures are mounted on a turntable and suspended from a piece of tightly twisted hair/ plant fiber. When the fiber is dry it tightens and twists the turntable one way. The woman is places in such position on the turntable that it comes forward in this case. When the fibre is wet, it loosens and twist the turntable other way, the man comes forward in this case.
Another such model was made by Louis Ullman of Nashville, Tennessee in 1859. It is made of a box that has twisted plant fiber inside. The plant fiber is usually of orange and others that were specified in the patent. The box is exposed to air so that moisture can get in. When there is moisture the fiber loosens and when the humidity is low it is tightens. The fiber is connected to a pointer that moves around dial. As the fiber tightens or loosens the pointer move around the dial showing the level of humidity.