Salt at Montem

Will you allow me, as an old Etonian, to ask the derivation of "salt," as it used to be applied to the money collected at Eton Montem for the Captain of the Colleges? Towards investigating the subject, I can only get as far as *Salt* Hill, near Slough, where there was a mount, on which, if I remember rightly, the Captain waved a flag on Montem day. A brief account of the origin of Montem would be interesting; and it is especially worth noting now that the pageant is suppressed.