This rare word refers to ‘a new year’s present to wish good luck’, or a foretaste, as used in George Herbert’s poem ‘The Holy Scriptures I’:

‘Thou art joy’s handsell: heav’n lies flat in thee / Subject to ev’ry mounter’s bended knee.’  

Source: George Herbert (1593-1633), quoted in John Drury,Music at Midnight: The Life and Poetry of George Herbert (London: Penguin Books, 2014), p. 9