surco.

macuili çorquito = 10 small furrows
(San Pedro Tototepec, Toluca Valley, 1733)
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 104.

Caxtoli ÇorCo = 15 furrows
(San Pedro Tototepec, Toluca Valley, 1733)
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 102.

niccahuilia Ome Surco metotontin = I leave her 2 furrows of small magueyes
(Santa Clara Cozcatlan, Toluca Valley, 1731)
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 60.

In Toluca, the term surco referred to a plot of land that was smaller than those plots that were measured in quahuitl.
(San Pablo Tepemaxalco, Toluca Valley, 1731)
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 26.

Cepoali surcu = 20 furrows
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 153.

25 surcos are mentioned as part of "se tlalin" = a piece of land measuring 5 quahuitl (translated as palos); these were sold by a family man to his niece for 7 pesos(Tenango del Valle, 1749)
Stephanie Wood collection, notes from Nahuatl documents in the file "Bills of Sale," citing AGN (Mexico) Tierras 2545, exp. 11, f. 5r. (Spanish translation appears on f. 4r.)

quimomaquilis caxtoli xolco = que le den quince surcos (Santa Ana Acoltzinco, 1673)
Vidas y bienes olvidados: Testamentos indígenas novohispanos, vol. 1, Testamentos en castellano del siglo XVI y en náhuatl y castellano de Ocotelulco de los siglos XVI y XVII, eds. Teresa Rojas Rabiela, Elsa Leticia Rea López, y Constantino Medina Lima (Mexico: CIESAS, 1999), 194-195.