The forty-first hexagram, Sun ("Decrease"), places Gen (Mountain) above Dui (Lake). The lake at the foot of the mountain is deepened by giving up some of its own substance to enrich the heights, the image of the lower diminished to benefit the higher. It follows Deliverance in the King Wen sequence.
Sun holds a further position in the xiantian, or Earlier Heaven, arrangement, the binary ordering devised by Shao Yong in the eleventh century and traditionally ascribed to Fu Xi: fifteenth of 64, apart from its forty-first place in the King Wen sequence above. This was the Fu Xi ordering that the Jesuit Joachim Bouvet sent from Beijing in 1701 to Gottfried Wilhelm Leibniz, who recognized its broken and unbroken lines as his own binary 0 and 1.
Read from the bottom, the six lines of Decrease run yang, yang, yin, yin, yin, yang. A later interpretive layer absent from the original Zhou Yi, the nuclear hexagram (hu gua), treats lines two through four as a lower trigram and lines three through five as an upper one; here they combine as Kun over Zhen, forming hexagram 24, Return (Fu), a hidden figure first associated with the Han-dynasty scholar Jing Fang, whose Yijing commentary of the first century BCE is credited with the earliest appearance of nuclear trigrams. Decrease's King Wen partner is hexagram 42, Increase (Yi); most of the sixty-four pair this way, related by turning the whole figure upside down, while the eight hexagrams built from a single doubled trigram pair instead by inverting every line. Mawangdui (1973) orders hexagrams by trigram, not King Wen; names here follow Wilhelm and Baynes, 1950, not Legge, 1882.