Setting up budgets for project includes both purchases as timesheet. However, the budget view in accounting seems to be able to add budgetary positions for either timesheets or purchases, not both.

One can give a budget in that case of the total costs to be expected, but not split into effort (timesheet) and purchases. 

In case the planned hours are indicated in the Project / Task view, these planned hours do not appear into the budgeted amount.

Is there a way to define a budget which details the difference between timesheet and purchases (budgetary positions)?

With other words, can a budgetary position be created only based on timesheet recordings?