The poem inscribed on these bowls, Sanqing cha (Three Purity Tea), was one of the Qianlong Emperor's favorites, and described the tea made from plum blossoms, finger citron and pine nut kernels, and further describes the virtues of tea making. Each New Year the emperor would hold a tea-drinking banquet in the Forbidden City and his guests were invited to compose poetry.
The present bowls are related to very similar bowls with Qianlong iron-red seal marks, such as one in the collection of the National Palace Museum illustrated in Emperor Qianlong's Grand Cultural Enterprise, Taipei, 2002, no. 51, and another in the Palace Museum, Beijing, illustrated in The Life of the Emperor Qianlong, Macao Museum of Art, Macao, 2002, no. 79. Three other bowls of this design are illustrated and discussed by P. Lam in "Tang Yin (1682-1756): The Imperial Factory Superintendent at Jingdezhen", T.O.C.S., vol. 63, London, 1998-99, p. 69, fig. 4. See, also, the similar bowl with Qianlong iron-red seal mark sold in these rooms, 20 September 2005, lot 347.
The present pair of bowls appears to be the only known examples of this design bearing the hallmark, Xiqing Tang zhi (made for the Xiqing Hall). This hallmark is recorded by G. Davison in The Handbook of Marks on Chinese Ceramics, London, 1994, pp. 72 and 173, no. 652, where the author attributes it to the Daoguang period.