Some Horseshoe Sum
Then what you say to this equation? If I sold unto you an horse having 4 shoes, and in every shoe 6 nayles, with this condition, that you shall pay for the first nayle one ob: for the second nayle two ob: for the third nayle foure ob: and so forth, doubling until the end of all the nayles, now I ask you, how much would the price of the horse come unto?
Solution:
Source: Robert Recorde's Grounde of Artes (1541)
