सिद्धान्तदर्पण (महामहोपाध्याय सामन्त चन्द्रशेखर सिंह - नग्न-नेत्र खगोल वेध एवं गणित महाकोश)

xxii सिद्धान्त दर्पण
made of the pericarps of the Bottle-Gourd
(Lagenaria Vulgaris) with water and mercury. But
it was more of the nature of a curiosity than of
much practical use. The instrument, of which he
made constant use, was one devised by himself.
This, which he is fond of calling his Manayantra
(measuring instrument), may be properly called a
tangent-staff, it consists of a thin rod of wood,
twenty-four digits long, at one end of which is fixed
another rod at right angles in the form of a T. The
cross-piece is notched and also pierced with holes
at distance equal to the tangents of the angles
formed at the free extremity of the other rod. Of
course, such a rude instrument did not admit of
being so divided as to enable him to measure a
degree with any accuracy.
But it is a real pleasure to see him handling his
Manayantra with a precision marvellous to behold.
Constant practice has given him such facility with
it, that he would not care to have recourse to his
other instruments although better suited for
measurement of vertical angles. Indeed, in most
cases, mere inspection is often sufficient to enable
him to hit the angle to the nearest degree.
One instance of the perfection he has attained
by practice came before us when I saw him for the
first time. Some of my friends doubted his
pretensions to practical astronomy, and were
desirous of testing his knowledge. One evening
when Mars and Venus were about 6° apart in the
western sky, he was requested to show, if he could,
with the help of any improvised instrument the
actual distance between the planets. After a
moment’s pause, he made his manyantra out of a
stick 42 digits long, attaching a crosspiece of 4-1/2