A contemporaneous oral agreement to pay a certain rate of interest is not admissible under the Proviso, Section 92, Evidence Act if the document embodying the transaction of loan is a formally drawn up instrument e.g., where the instrument is a promissory note [Gopal Madhorao v. Achutsadasheo, 1941 N 271; Moti Biswas v. Haripada Pal , 70 IC 790; Kadir Baksh Hazir Bakshi v. Shaikh Srajuddin, 49 C 716; Yado v. Beharilal, 53 ILC 242: Lachmi Chand Jhowar v. Hemendra Prasad Ghosh, 18 CWN 1260; Pentaya v. Kasherorao, 56 IC 249], or a hundi [Kishore Chand v. Gurditta Mal, 52 PR 1911; Banwari Lal v. Jaggar Nath Prasad, 35 IC 431; Ram Gopal v. Sita Ram, 20 ILC 319], and is silent on the point. But in another case it has been held that, in the absence of any stipulation as to interest in a bond, oral evidence is admissible to prove a separate agreement about it. The evidence must, however, be very satisfactory and strong in order to establish such separate oral agreement when the bond is silent about it. [Rozario v. Hariballabh Onkarji Trivedi , 100 IC 794]. If the document is not a formally drawn up instrument but is a mere memorandum e.g., where the document is a hathchitha [Nabin Chandra Nath v. Debendra Mohum Mukhopadya, 36 IC 612; Umesh Chandra Baneya v. Mohini Mohu, Das, 9 CLR 301], or an entry in a bahi [Bhan Singh v. Gokul Chand, 1 L 83], or a sarkhet [Lachnil Rai v. Srideo Rai, 1939 AWR (HC) 79], an oral agreement to pay interest is admissible. It should, however be noted that evidence of a contemporaneous oral agreement contradicting or varying the rate of interest mentioned in a document is inadmissible, [Gopal Madhorao v. Achut Sadasheo, 1941 N 272].