Yupana  A yupana (from Quechua yupay: count) is an abacus used to perform arithmetic operations dating back to the time of the Incas. The term "yupana" refers to two distinct classes of objects:   Although very different from each other, most of the scholars who have dealt with table-yupana, have then extended its reasoning and theories to the yupana of Poma de Ayala and vice versa, perhaps in an attempt to find a unifying thread or a common method. The Nueva Coronica was discovered only in 1916 in the library of Copenhagen and that part of the studies on it were based on previous studies and theories regarding table-yupanas. Several chroniclers of the Indies described, unfortunately approximately, the Incan abacus and its operation. The first was Guaman Poma de Ayala that in 1615 approximately, wrote:  In addition to providing this brief description, Poma de Ayala draws a picture of the yupana: a board of five rows and four columns in which are designed a series of white and black circles. The father Jesuit "José de Acosta" wrote:  Father "Juan de Velasco" wrote:  The earliest known example of a table-yupana was found in 1869 in Chordeleg, Azuay Province, Ecuador. It is a rectangular table (33x27 cm) of wood consisting of 17 compartments, of which 14 are square, 2 are rectangular, and one is octagonal. On two edges of the table there are other square compartments (12x12 cm) raised and symmetrically arranged one another, to which two square platforms (7x7 cm), are overlapped. These structures are called towers. The table presents a symmetry of the compartments with respect to the diagonal of the rectangle. The four sides of the board are also engraved with figures of human heads and a crocodile. As a result of this discovery, Charles Wiener began in 1877 a systematic study of these objects. Wiener came to the conclusion that the table-yupanas served to calculate the taxes that farmers paid to the Incan empire. Found at Caraz in 1878 - 1879, this table-yupana is different from that of Chordeleg as the material of construction is the stone and the central compartment of octagonal shape is replaced with a rectangular one; towers also have three shelves instead of two. A series of table-yupanas much different from the first, was described by Erland Nordenskiöld in 1931.