curl --request GET \
  --url https://test.deribit.com/api/v2/public/get_historical_volatility \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "id": 8387,
  "method": "public/get_historical_volatility",
  "params": {
    "currency": "BTC"
  }
}
'

{
  "jsonrpc": "2.0",
  "id": 8387,
  "result": [
    [
      1549720800000,
      14.747743607344217
    ],
    [
      1549720800000,
      14.747743607344217
    ],
    [
      1549724400000,
      14.74257778551467
    ],
    [
      1549728000000,
      14.73502799931767
    ],
    [
      1549731600000,
      14.73502799931767
    ],
    [
      1549735200000,
      14.73502799931767
    ],
    [
      1550228400000,
      46.371891307340015
    ]
  ]
}