Source : Agasthya Samhita ( 6th or 7th century BC)
samsthapya mrunmaye paatre taamrapatram susamskritam
chhadayet shikhigreevenaardraabhih kaashtapaamsubhih
In an earthen pot , keep a Copper plate ( taamrapatram ) and cover it with Copper Sulfate ( shikhigreeva ) and wet wooden dust.
dastaloshto nidhaatavya paaradaacchadistastata
samyogat jaayate tejo mitravaruna samjnitam
On top of that place a Zinc ( dastaa ) plate coated with Mercury ( paarad ). From this combination is produced an energy called Mitravaruna ( Electricity ).