Double rand hourglass but with one glass missing.
Licence: Attribution 4.0 International (CC BY 4.0)
Credit: Double rand hourglass but with one glass missing. Wellcome Collection. Source: Wellcome Collection.
Licence: Attribution 4.0 International (CC BY 4.0)
Credit: Double rand hourglass but with one glass missing. Wellcome Collection. Source: Wellcome Collection.