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Most of the previous studies have identified Brunelleschi's drafting method as the 3-plane method. The present author infers that his method was different from the 3-plane methods, etc. This paper is concerned with the conceivable Brunelleschi's method. The method the author propose is a simple method that uses the ratio of the viewing distance between the object and the screen. It is not described in the previous studies. It is conceivable he discovered his method from architectural surveys. Later in the paper the rule of inverse proportion in perspective drawing is proved.
Keiichiro NARIKIYO (Sat,) studied this question.