Section 59. Mortgage when to be by assurance

59. Mortgage when to be by assurance.— Where the principal money secured is one hundred rupees or upwards, a mortgage[5] [other than a mortgage by deposit of title-deeds] can be effected only by a registered instrument signed by the mortgagor and attested by at least two witnesses. Where the principal money secured is less than one hundred rupees, a mortgage may be effected either by[6] [a registered instrument] signed and attested as aforesaid, or (except in the case of a simple mortgage) by delivery of the property. 7* * * *