To hatch the eggs, it was necessary to keep them at a constant temperature of 21°C for 10-15 days, the period known as incubation.
In the past, there was a widespread belief that the ideal temperature was that of a healthy human body, so during the day, women carried a small container with silkworm eggs under their armpits or between their breasts. During the night, the container with the eggs was placed at the end of the bed.
Gradually, during the 19th century, this method was abandoned and the eggs were left day and night in the bed, inside a box covered with perforated paper, with a bed warmer being used to maintain the heat.
Later, for reasons of hygiene and to obtain a better result, the entire room was heated with stoves and burners. The advent of incubators led to significant progress in the entire process.