2016-01-01 open Assets:Checking
2016-01-01 open Equity:Opening-Balances
2016-01-01 open Expenses:Groceries

2016-01-01 txn "set opening balance"
    Assets:Checking         1.000,0001USD
    Equity:Opening-Balances

2016/1/5 txn "farmer's market"
    Expenses:Groceries     50 USD
    Assets:Checking