Infant

Séguin, Édouard. "Idiocy: and its Treatment by the Physiological Method", published in 1866. https://archive.org/details/idiocyanditstre00sggoog

This is the book on which Montessori has based her method. She recommends some of the gym contraptions (such as a special swing) from this book. (Starting from page 83).

"The Montessori Method" by Maria Montessori, published in 1911. This is the first book she published were she describes her method, and the history of arriving at it. https://www.amazon.com/Montessori-Method-Maria-ebook/dp/B00CBDC2U0/

====

Montessori describes the importance of sense training. She gives an example of a cook who is asked to buy fresh fish, but can't do so, because his senses are not trained to recognize what is a fresh smell of fish. Another example is a cook who knows the recipe but can't really tell by taste when the meal is ready, or when an ingredient must be added to adjust the taste, because her sense of taste is not developed. The point is that senses should be trained in childhood, not in adulthood, when it is much harder.

Here are items on Amazon for training senses:

baric sense: https://www.amazon.com/gp/product/B01LWICS7Q/

sense of touch: https://www.amazon.com/gp/product/B01LZFTTVK/

sense of colour: https://www.amazon.com/gp/product/B01M12CGY6 and https://www.amazon.com/gp/product/B00793NVTI

Note: teaching sense of colour in the beginning requires having the same exact colour in doubles. You show one colour tablet, and ask to pick the matching tablet of the same colour. The next stage is to teach gradient of the same colour.

Montessori recommends teaching the sense of sound by way of training to hear finer noises in absolute silence, for example the ticking of a clock.