The right way to introduce the funds in proprietorship is through capital only . You can withdraw it when the funds are available or business is in profits
There are certain Accounting Concepts 1) Business entity concept 2) Money Measurements Concept 3) Cost Concept . Almost all Business entity have accepted Business Entity concept , wherein Business and Business owner are two different entities for accounting purpose , So anything invested in the Business , same is the Liability of the Business to pay back , similarly anything withdraw from Business will be treated as Drawings by the owner and payable to back the Business . we have to follow accounting concept , one of them is Business Entity concept followed by also most all Business.
Proprietors capital is a liability in the business as well. But showing it as a loan might be correct from accounting standard view point but not logically. It's like choosing theory over practical approach.