Incubate Like An Egyptian

At around 3,000 years ago, the early Egyptian incubators consisted of a large mud brick building with a series of small rooms (ovens) located at each side of a central passageway.  In the upper part of these “small incubation rooms”, there were shelves for burning straw, camel manure, or charcoal in order to provide radiant heat to the eggs below.  Vents were located in the roof of these cambers, and they allowed smoke, and fumes from the fires to escape and also provided some light.  The entrance to each incubator room from the passageway was through a small manhole. 
Thousands of eggs were placed on the floor of each incubator room, and they were turned twice a day.  Temperature control was achieved by controlling the strength of the fire, the opening of the manholes, and by regular openings of vents in the roof of the ovens and passageway.  Humidity was controlled by spreading moist jute over the eggs when necessary.  
In this rudimentary incubation system, the temperature, humidity, and ventilation were checked and controlled without using measuring devices like thermometers.  It was done by having the hatchery manager and the hatchery workers actually living inside of the building.  By living there, they would soon learn to judge the humidity, temperature, and air freshness using their own feelings, and their sense of touch.  In other words, they were able to detect any deviation from the standard.  It is  recorded, for example, that they used to test the temperature of the eggs by holding them against their eye lids (the most sensitive part of the body) for judging temperature.