When a biz owner pays a business expense from his/her personal funds, the treatment on the company's books could either be a payable to the owner (as Kirby suggested) or a capital contribution by the owner, recorded on the balance sheet as equity.
Which treatment is chosen depends primarily on the owner's intention as to repayment: If he intends to reimburse himself pretty soon from company funds, I'd set it up as a short-term payable on the company's books, pending reimbursement. If OTOH the owner is viewing his expenditure as a form of contribution to the company's capital, then the latter treatment would be more in alignment with that thinking.
In this particular case, PHoffmann used the terminology "...as an initial investment..." and so I'd be inclined toward the treatment suggested by Penpusher.