No nuncupative will shall be valid where the personal estate bequeathed exceeds in value one hundred dollars, unless declared in the presence of three witnesses who were requested by the testator to bear witness thereto, in his last sickness and in his usual dwelling, except when he was taken sick from home and died before his return; nor unless a memorandum thereof was reduced to writing within six days, and presented for probate within six months from the making thereof.