Four methods were employed for obtaining recruits for the system,—by capture, purchase, gift, and tribute. Of these only the last is commonly considered;[84] but it was originally, and probably always, merely supplementary to the others.[85] The four methods ultimately rested on two. Slaves who were bought for the sultan or given to him had nearly all been either taken as captives or levied illegally with the tribute boys; there was hardly any other way, since slaves passed too rapidly into the Moslem fold to have their children available for the system. As to the comparative numbers obtained by the different methods there are few data for calculation. Probably about three thousand tribute boys was the annual average in the sixteenth century,[86] but there is no reason to think that this was a majority in the number of annual recruits. The whole number in the system may be estimated at about eighty thousand.[87] Since the losses by war were sometimes tremendous, it is probable that the average annual renewal required was as much as one-tenth, or between seven and eight thousand. On this basis the tribute boys furnished somewhat less than one-half of the whole number. These calculations are, of course, more or less arbitrary. It is true that children of _Spahis_ of the Porte might be admitted to the college of pages at the pleasure of the sultan, but their grandchildren and the children of all other Moslems were excluded by rigid rules.[88] These rules began to be invaded about the close of Suleiman’s reign by the admission of the sons of Janissaries,[89] an innovation that was of ultimately fatal import to the system. A certain number of adults were also received and some of these were sons of Moslems; exceptional individuals from among the irregular troops were admitted to the _Spahis_ of the Porte by way of reward,[90] and that body contained a Foreign Legion of about two thousand, composed of renegade Christians, Arabs, Nubians, and the like.[91] Occasionally, also, some high official of Suleiman’s government had been born a Moslem.[92] But the total effect of all these exceptions was so slight as to cause them to be disregarded by more than one contemporary observer.[93]