Ancient indian Text "Agastya Samshita" dates back to the first millennium BC. It contains a detailed description not only of how to construct an electric battery/cell, but also, how to utilize the battery to 'split' water into its constituent gasses.
Modern battery cell resembles Agastya’s method of generating electricity. For generating electricity, Sage Agastya had used the following material: One earthen pot, Copper plate, Copper sulphate, Wet saw dust, Zinc amalgam
His text says :
संस्थाप्य मृण्मये पात्रे ताम्रपत्रं सुसंस्कृतम्। छादयेच्छिखिग्रीवेन चार्दाभि: काष्ठापांसुभि:॥ दस्तालोष्टो निधात्वय: पारदाच्छादितस्तत:। संयोगाज्जायते तेजो मित्रावरुणसंज्ञितम्॥
“Place a well-cleaned copper plate in an earthenware vessel. Cover it first by copper sulfate and then moist sawdust. After that put a mercury-amalgamated-zinc sheet on top of an energy known by the twin name of Mitra-Varuna. Water will be split by this current into Pranavayu and Udanavayu. A chain of one hundred jars is said to give a very active and effective force.”
When a cell was prepared according to Agastya Samhita and measured, it gives open circuit voltage as 1.138 volts, and short circuit current as 23 mA.